You don’t necessarily need a removal spell if you have a creature that would eat it, since it has to attack each turn. Rest of your points are solid though and probably relegates it to SB material for aggro mirrors.

There are a few issues with Shedder. The first is setup. You can’t just drop Shedder on T1 and then go to town on subsequent turns with countermagic and removal backup. You can’t even CAST Shedder on the play on T1 (sans Spirit Guide). Even once you get Shedder up, you still have to kill the opposing creature, which depends on drawing that removal and resolving it.

A much bigger issue is Shedder’s uselessness in creatureless matchups. Tron, Ad Nauseam, and different Grixis Control and Jeskai Control lists aren’t going to have early targets for this card. This means Shedder isn’t coming online until much later, if at all, in about 10%-15% of matches. Other decks, such as Jund and Abzan, won’t always play early creatures, so now your landlocked Delver isn’t even getting online until after a Goyf, Rhino, or Lily is down.

All of this points to Shedder maaaaybe being sideboard material, but probably not maindeckable.

The development cycle is really far ahead of the ban cycle. Or behind, depending on how you look at it. Pod got banned in January 2015, at least 6 months after DTK development was finalized (which itself was probably 2-3 months BEFORE Rhino broke Pod). So although I’m annoyed Shadows didn’t give Modern as many control tools as it deserves, I don’t think this is a Wizards failure. It’s just not realistic to expect otherwise, unless we are claiming they knew they were banning Pod about 8 months ago.