I think (after reading what they wrote) that both the positive and negative critics have some good points, but overall this is a decent and charming film for very little kids. I'd put it about on par with one of Kachanov's early films, "Novice" (1961). The screenplay does a good job of expanding the original basic fairy tale by giving some more characterization to the bears before the scenes with the fox happen, while the art direction does try a bit too hard to be "naturalistic".
It was a decent start to Soyuzmultfilm's puppet tradition, even if it isn't as good as the films of Starevich in the 1910s or Ptushko & co. at Mosfilm in the 1930s.