Polar bears SHOULD have an AC of 12, although canonically they *DO* get 42 HP and two attacks, so the polar bear form is nerfed in BG3, while land druids can wildshape WAY more efficiently than they should.
But the wildshape is still awesome. It's a free buffer of HP, and you can damage AND take attention from enemies while your party moments get free shots, so it's still insanely good. I don't personally mind that the polar bear is nerfed a bit, since they DO at least get the "goading" ability that enables them to soak while the others are safe to do their thing. I don't like that moon druids are now weaker compared to land druids, who gets way better wildshaping than they should.
But then, I am not too happy about 80% of the homebrewing that Larian has done so far. I sincerely hope they will make things far more DND in the future.