I also love 2d platfomers and mertoidvenias,they are my favorite kinda games of all time , but my "dislike" of the platforming comes mainly from the use of the mouse to grow the plants ( whichwas difficult with the moving camera,when the camera was zoomed out, just like one of the levels, I didn't have a big problem but most of the levels aren't) and I just prefer a more weighy jump ( that you can control by how much time you press the jump button) in general , the physics just feel very rough, I wonder if you're using the default values of unity's rigidbody .I prefre my jumps snapey like hollow knight and celeste but if you personally like it that way then so be it.
The reason that you have a hard time noticing the backround problems is because you have been working for this game for 2 whole weeks, what you consider normal and intuitive might not be for someone like me, because with time I easily understood what the interactable areas are, but this is still a problem especially if you add more assets, or just for color blind people who will not notice the color difference at all, they need a place to be darker than the other, like how this text is black in a white backround and if you make them a similar value. people will have a hard time reading, so just make their life easier and have more contrast. But that's just my opinion off course .
You still did a good job and it's very cool that you put your assets for free, am sure that someone will find them really usefull.