It seems to be a bit too gimmick/setup heavy, with all those player blocks, NPC blocks, NPC remover, and colored switches. Not that it isn't bad, it is just a bit visually unappealing. It is quite apparent in the underwater maze-like segment with the keys, or the vast number of custom blocks on the surface. You don't need the colored switches for the setups since you barely activate some to unlock the paths. There is a better way to implement the setups without making the terrain look weird.
There is a lot to handle. Wooden planks that you can spin and jump on, arrows/powerups that pop bubbles, underwater Hammer Sharks line guides, etc. I rather you focus on one or two before having setups that bear no relevance to the others. Star Coins too, are just there to collect without directly related to the gimmick. And the alternative path that takes you underwater for the second half of the level too...
The boss too has some problems with how you set it up. If you are capable of making such a boss HP bar, you can make it better. For instance, the bricks to prevent hitting the boss multiple times (even though it didn't work once), the stage layout design (not center-aligned), and the boss itself. It doesn't attack the player, so it is kinda boring to throw the bricks multiple times with increasing projectiles from the Lotus plants.
You can rewatch your video. There are certain places you got stuck on, or even cause the level to freeze. Levels with technical problems (such as lagging, freezing, crashing, etc) get deduced with points. So be careful of that.