So at first, I thought "Hm, not much of a Metroidvania, just a platformer really." But then there was backtracking! I think having to move along with the moving platforms is fine -- it's an extra challenge where otherwise I would just be waiting to jump to the next one. Having some small progression of player abilities would have really solidified it into the Metroidvania genre you were going for. Maybe adding a double-jump that you acquire in one room and need to get to another? That could replace the keys as a way to gate progress. It would also open up more possibilities for platforming challenges. As it is, the challenges on offer are a bit samey.
Overall, great work on this submission. I think you definitely have a foundation here that you could build on, if you wanted. :)