im a fellow game dev and here are my critics: bad controls for switching weapons, hard to learn hard to master. The gravity dash thing sucks, it is one of those useful mechanics that I could see a ton of players not using because of how unintuitive it is and its introduction also leads to a few deaths that do not fell like the players fault and would have players write the mechanic off in its entirety. The tutorials are so so bad and need check points, they also need to be more constrained because I could just use the fist to skip everything in every tutorial so I would fix that too. all these things in conjunction would make a large part of your potential player base return the game after 30 mins to an hour.
I liked the demo because I like movement based but I mostly just ran around the sandbox because the levels were not designed to be as straight forward as they should have been, you should make a few levels before that like e1m1 that are really straight forward than introduce all of the other mechanics. no hate in any of this, take this all with a grain of salt, gl