It's very unfortunate that Polar Bears were added in a rushed Development Stage where Mojang just wanted to push content quickly after the long waited 1.9 Combat Update.
I understand their intention was get this Update
(1.10) done and try to prevent Updates take long time to develop, but this decision came with some consequences which I consider the Polar Bear suffered badly, while we got recently Pandas with fancy and interesting Personalities and now Foxes with really intriguing AI.
Polar Bears still there as a closed Project with a flat and boring feeling,
I believe a little and closer look at them to improve some things (Just like Skeletons getting AI overhaul in 1.9) can make this aesthetic Mob interesting and serve properly as their main purpose, which is give the game more life aesthetically. Maybe adapt the new Fox Hunting-Fish mechanic can improve significantly the feeling that Polar Bears can give.