This game has serious potential, so far one of the best I've played this jam. You've accomplished a lot for the jam but I think what's important is you have the bones here now for a really fun game when more fleshed out. Just some ideas off the top of my head from similar games, it would be interesting if there's some type of elements that resize differently compared to other ones, highlighted with a unique color or texture. The player's all cozy playing the game and then ooooh shiiii this block doesn't change the same way! An exciting new challenge. Also it would be funny if you resize in a way that squishes the guy, he gets squished and you gotta restart, so you have to be a bit more careful.
I think the most important thing is to find a way to make the window resize mechanic fully keyboard / controller compatible, so not just resizing by mouse. Maybe you can find some inspiration from window managers like i3wm or popOS shell? Resizing windows is a very solved problem in linux desktop environments / window managers and so you could find some interesting resize mechanics there.
I'm not sure if it was a bug but I had multiple windows open for multiple levels at once which I really enjoyed, there's some seriously sick complexity you could integrate there. Imagine if there was also a mechanic to move windows around and jump between them!