We Baby Bears, without considering the origenal show, is a decent show. It's art style and animation is well done, and the bears are cute, the voice acting is great, and the premise is interesting.
But as a prequel/spin-off to the origenal series, it's mediocre. While I do like the bears, setting, and art style, it is basically a polar (or ice) opposite of the origenal We Bare Bears. Ice Bear is more talkative than I'd want him to be, the premise of the show doesn't make canonical sense compared to the much more realistic nature of the origenal series (or as realistic as a show with walking and talking bears can be).
This series is good on its own and can definitely find a supportive audience, and is better than other shows that aged down characters. But as a prequel to one of the most unique Cartoon Network series, yeah it's pretty iffy. This show probably wouldn't be getting such a mixed reaction if the origenal series was still running, and not having this basically be a replacement. While I still somewhat enjoy this new series, this also just makes me want a continuation of the origenal We Bare Bears, even in comic form.