Right now, Standard is more stale than that half loaf of bread you straight up forgot was in the cupboard from god only knows when. Its been so long that you can't even exactly pinpoint how old it is. So, you throw it away and move on with your life. No harm, no foul.
I think that a lot of people have pretty much taken the exact same approach to the current Standard format. Toss it out and wait for somebody to bake a hot fresh format in the future.
I'm not exactly sure why people have given up on Standard. There are several perfectly plausible reasons mind you---I'm just not sure which one is having the greatest effect that is leading to people to abandon the format faster than a sinking ship.
The Illusion of a One-Deck Format
Most formats boil down to a point where it becomes the myth that one deck is the best. In this case, that deck is pretty clearly Bant Company. The pro opinions that players read in articles is pretty biased toward, "Bant is the best." For good reason---that statement is certainly true.
However, every format always has a best deck or two. It is part of how metagames work. The last format had 4C Rally and before that it was Abzan. The best deck is certainly beatable in matches of Magic. I actually think that from a game play perspective Standard is pretty great. Bant may be the best deck but it actually has bad matchups against the Emerge decks and can certainly be beaten by the Delirium Emrakul decks. The games are fun and interactive.
I think the problem here is that saying Bant is "the best deck" is both true and easy for MTG writers. Readers don't always understand the difference between "the best deck" and "the only deck." Which makes the format sound unattractive.
Another problem: if there is a best deck why wouldn't I just play it? Well, I do play Bant Company in every Standard event and have for the better part of a year. The problem isn't with me playing Bant Company (or even Standard for that matter) but rather with the more casual crowd. If the FNM and PPTQ level players confuse "best" deck with "only" deck they might not find a world of Bant Company mirror matches to be very appealing.
The matchup is difficult, complicated, and hard to maneuver. If I were a newer player still learning the ropes I would not find a format full of this matchup to be very appealing because I probably wouldn't win very much. Even if you were new and savvy enough to figure out that Temerge was Bant's "bad" matchup things are dicey because Temerge is much more difficult to play well than Bant!
I think in this case the perception that Bant is the only "real" deck choice has really hurt the popularity of Standard.
Summary: People think Standard is an only-deck format that isn't worth playing. Standard is actually a really fun and dynamic format that is worth playing but people are sitting the season out.
The Move Towards Quicker Rotations
I think the fast Standard rotation, while initially met with a lot of optimism, is having a real negative effect on Standard. The fact that cards fall out of Standard much more quickly makes it much more difficult for players to justify investing time, energy, and money into buying and having a Standard collection.
Before, players knew they would get a lot of mileage out of their Standard cards. Multiple years' worth of entertainment and game play. However, now cards are here and gone in a year and a half. The cost of playing Magic is a serious issue with the majority of players who play and attend local events and faster rotations certainly increases the cost to show up and play.
Fewer legal sets and faster rotations also causes the format to shift and change much more quickly that it did before. Rotation doesn't only affect the value of the cards that leave the format, but also the value of the cards that were contextually good because of cards that rotated. So, when Collected Company rotates in the fall it will also drastically influence the price of the cards that got played alongside it.
So, players discover that while their Sylvan Advocates and Tireless Trackers may still technically be Standard-legal post-rotation, they will still need to either buy new supporting cards or switch to a new deck. Every rotation will typically create new decks and require players to make another serious investment.
Players are less invested in actually playing Standard because it changes too fast and requires too much time and energy to keep up on and too much money to play.
Summary: Players are figuring out that faster rotations significantly increase the cost of playing Standard because decks need to be replaced much more quickly. More people are opting out.
Lack of Meaningful Events
I didn't go to Pro Tour Eldritch Moon, which means there was literally only one Standard event that included Dragons of Tarkir and Eldritch Moon on my schedule for the entire season. I played in exactly one RPTQ.
There were really not very many events to get excited about with this Standard format. I mean, there is always local stuff and FNM but there were not many GPs or other travel-worthy events that players would be excited to test and practice for. When that interest isn't there a format can really feel lame.
It creates a feeling where people ask themselves: "Why am I even bothering to play this format? There is no endgame." It is totally lame-duck. Kaladesh will arrive. Dragons and Origins will rotate and we will all buy new decks.
People have enjoyed lame-duck formats before. In fact, there were a lot of Standard formats where attendance for local events was high straight through until the end because players enjoyed playing the format. Clearly, this is not the case right now.
Modern is the Truth
I think it is also very true that Modern has really caught fire. Pretty much everybody who attends tournaments at all of my LGSs owns a Modern deck. Seriously, everybody owns a Modern deck these days.
That observation signifies a couple of things to me. Firstly, Modern is a great format and the games are a lot of fun. People enjoy playing Modern more than they enjoy playing Standard.
Secondly, a big part of the reason they enjoy Modern is that since the decks never rotate they get a chance to become more intimately familiar with their decks. It takes a lot of reps to become decent with a deck and in a Standard where decks are constantly being shaken up by new releases and rotations things change a lot faster. If you think about it, if there are eight sets in Standard, one new set being released constitutes a relatively small percentage of the card pool and will have a slight effect. However, if the format is four or five sets one new set is going to drastically alter the landscape.
Too much change is off-putting and makes players feel like they are starting all over. I agree that in principle more rotation should keep things fresher and changing around more. The last thing anybody wants is for Standard to get boring and for players not to want to play it. However, it also appears that too much rotation adds significant cost to maintaining a deck. It also adds a higher learning curve because players need to learn a lot more format-related information in order to be able to seriously compete.
Modern mitigates a lot of this downside because once you buy into the format you have a deck forever (sans a banning). The format changes very slightly and very slowly so there is time to learn about your deck and the matchups against other decks.
Last but not least, Modern never rotates which means the value of your collectible cards doesn't plummet after owning them for about a year! In fact, most of the cards in Modern appreciate in value all the time.
So, let me get this straight... The cost (in time, energy and money) to play Standard increased dramatically and after it is all said and done my cards plummet in value? Or, I could just play Modern where my cards increase in value all the time.
Summary: I think a lot of players prefer Modern to Standard. The new rotation format also makes Modern a more attractive option for a lot of players.
Will Kaladesh Save Standard?
If the assumption is that the reasons people are not playing Standard are that there are no events that matter and that they are afraid of Bant Company then I think there is a chance that Kaladesh could breathe new life into Standard. I mean, it would be hard for a Standard format to have lower popularity or enthusiasm from players than the current one.
The thing that worries me is that if the lack of interest is stemming from a significant portion of the player base refusing to participate because the price to play went up significantly, it could have really big implications down the road. It could mean potentially less product sales for WoTC. It is also worth noting that it could also lead to dwindling singles sales for LGSs and online sellers. I can certainly attest to the fact that Standard prices are way down and sales on Standard cards have been very low at my LGS over the summer.
There is always a chance that Kaladesh will have a bunch of sweet cards and people will be very excited to play Standard. Yet, wasn't Eldritch Moon a super sick set full of powerful awesome cards? Isn't Standard actually a very dynamic format full of cool decks and fun-to-play games?
Summary: I think there are a lot of reasons we can look at to explain why Standard is not popular right now. However, my gut tells me that the new rotation is playing a bigger role in this trend than many people seem to think. I'm not sure that the problem with Standard is one that Kaladesh can or will actually fix.
Note that Wizards won't just let their business model tank into the ground without addressing any lower sales figures or tournament attendance. So whatever problems may be caused by the current rotation model will probably be temporary. But as speculators it's important to keep abreast of the meta-changes surrounding the game's economy, and act accordingly.