So I get why people turns up their noses at 5e Polymorph. The INT alteration suck most of the fun out of getting to be a big monkey, especially since it is tailor made for bad DMS to abuse you with.
Sure In: 7 is low, but it's not THAT low. If cast on a fighter/barbarian that used INT as a dump stat it could barely register as a difference, especially since personality is kept. And it's a REALLY good emergency heal spell (with a fairly large caveat of caster's concentration - but still).
Now for other purposes, say trying to turn someone into a bird etc. to help scout? Then the spell is going to disappoint.
IMO polymorph is a great spell. Huge beneficial (or detrimental if cast on a foe) effect but just enough downsides to not really be overpowered.