I'm of the opinion that they didn't push it far enough.
No spell type is as wonky and unwieldy and filled with '2e-isms' as the Polymorph spells, for instance. I've removed the spell, and replaced it with a few spells spanning the levels that change the victims into various things (from turning things into, say, halflings at early levels, to goblins or pigs or toads or pumpkins at higher levels).
Also wonky spell-wise is the whole "(Blank) Person" tradition, which is a hold over from earlier additions. Right now, playing something non-humanoid of not small or medium size is remarkably unbalancing because it gives you effective immunity to a host of spells...it shouldn't be this way, IMHO.
I don't see many *mechanical* problems, though. The Ranger is front-loaded (but balanced). The Bard is kinda limp-wristed (but still balanced). The Monk isn't the combat machine people want it to be (but is still balanced). Harm is inordinately powerful (but balanced). Haste....well, I'm of the opinion that the problem isn't in the spell, but in the implementation (which, again, carries baggage from earlier editions). Heck, even the Ranger is a hold-over from 2e.
So, in other words, they didn't go far enough. Much of the problems I see are hold-overs and traditions. Which had it's advantages at first, but really starts to grow stale with age.
