On one hand I want them to keep that insanity so we can rampage as dinos, but on the other that is unbalanced and something that should be avoided from a game design perspective
The thing is, most of this stuff is already fairly well balanced in 5e. By messing with the fundamental mechanics of how things work, Larian throws that balance off.
Conjure Woodland Beings is a concentration spell - if you're focusing on keeping those pixies around, it limits the things that you can do (nothing else that requires concentration) and makes you a juicy target for enemy attacks. And just because pixies can cast polymorph doesn't mean that it will work against an enemy or that it's the best thing to do in the moment.
In 5e, familiars (which are generally not supposed to be able to attack, except for Pact of the Chain familiars) and Mage Hand do not require concentration. They aren't mutually exclusive and they don't exclude anything else. By messing with the basics of how they work, Larian has dramatically reduced the strength of two already-fairly-simple utility spells.
I'd love to see them implement the 5e rules as they're actually written - many things about this game feel very broken in places where they have deviated.
