Love the concept, really interesting idea. Simple, yet effective, the best kind! I did find it a bit frustrating to start up a path that would dead-end or just be out of reach of another path. I feel like being able to jump the full height of a block would be nice, as I found myself next to a block many times that I couldn't jump on to.
I'd also recommend tweaking the shadows/lighting. The light seems to be coming across the playfield, so it's kind of impossible without looking up all the time to know that a block is about to land on you. The shadows really need to be like directly projected onto where the block is going to land, so as the block approaches you from 10seconds above or something, you see the shadow below your feet indicating where you are is no longer safe to stand.
As fun as the block all falling down straight from above are, I feel like if they fell ahead of me forming paths out in front of me (as the lava rose forcing me along them) would make it easier as the player to look for opportunities and options to progress by being able to keep my viewport focused in one area as I try and move. There was just a lot going on to make it hard to understand where to look and where I should be going with all the constant movement in the so much space around me. Though I also see this allure of the continually higher structure, but again being able to know I had to move was key, and either some smarter generation or slightly more jump power to be able to better traverse across to more paths would be nice. Like I'd rather have the challenge of trying to just jump up the "mountain" and getting higher and learning how I can stretch my jumps vs. getting trapped on a dead spire and having to backtrack.
Like I never saw how I'd make it to keep up with new blocks. I wonder if waiting for the player to be near the highest placed block before a set of new blocks fall would be interesting too?