1) Talking about art and graphics without showing or explaining what you mean feels strange. If there is a background that is busy I won't know because you didn't show it or tell me of it. You saw it and just said "Backgrounds are busy" but which ones? Every level? Then the only recourse to fix it is to go into every level and assume the average persons ability to find each background busy when my eyes don't do that I'm bothered by NOTHING hence why I couldn't notice the busyness myself and need feedback on the subject probably making them that busy in the first place.
2) "INTERACBLES" is what you said and I couldn't understand that since I just call them puzzle cubes. Interactable doesn't make sense because there is tons of interactable stuff other than push blocks. The game has that attempt to be a mix of 3D platforming and sokoban but I guess I find sokoban push block puzzles fun and others don't you wouldn't be the first to mention something similar. Despite the genre of the game being a sokoban; I'm gonna try deleting all normal push block puzzles that are only meant to be pushed out of the way then but keep the special ones that have a bomb, laser, or fake boku attached to them then if they are more fun and put one more of those kinds of puzzles then instead on every level that's meant to kill enemies then if that fixes the problem.
3) When you say "more utilization of the other mechanics, especially the movement." that's extremely confusing to me again; there is moving platforms, plenty of ladders, lots of verticality level design of going up, falling down, fall blocks, you name it despite being grid based the levels design do a lot with 3D movement mechanics I'm confused. Dashing over gaps itself is another movement mechanic used a ton on every level for both gap traversal and killing enemies. Complex movement along the tile system happens a lot like with the land mines on 1x1 tiles in the snow cave level.
I think il just have to retool the boss then and make it like a more traditional game boss with a health bar and 5 attacks it can do at random in its arena's along with the patrolling; then you use a special cube to damage it in some form till its dead getting its health bar down and then you save a bunny cube instead of toggle buttons to unlock gates that lead to a giant puzzle cube that kills the boss like before.