The bug:
The block breaking animation appears darker than it should, making it look pasted on, and not at all like cracks in the block. I think this goes as far back as MCPE 0.8.1 (maybe). In very old versions of Pocket Edition, the block breaking animation appeared correctly.

How to reproduce:
In survival mode, break a block. Note that the block breaking animation appears almost black, when it should blend with the blocks colors and appear like cracks.

This is how the block breaking animation appears now: Minecraft 2021.03.06 - 15.14.04.13_Trim.mp4
This is how it should appear: Base Profile 2021.03.06 - 15.13.29.12_Trim.mp4
The comparison image below was used in a similar bug report from years ago. The bug was marked as "cannot reproduce" which I don't understand. I hope this issue is reconsidered.