A game for if you like the process of critiquing a game. Otherwise I feel as though your seeking to small of a target of player retention. I know some of us get kicks out of deluding our devotion, but people are gonna pass on this hard.
I do like the snippets of what you do use to keep the player around, but you really gotta either spread the butter or lay it on deeper. i get the jump scare is placed in a section to beat an early solution, but you could get more depth out of a few more tricks up you sleeve. The game follows the same idea as something like I Wanna Be The Guy, but your trying to punish and confuse the player on an even deeper and darker level.
You need more depth in play and I know you'll reach that over a larger sections of levels, but with my review I hope you choose to tinker with fitting more diversity and thought into the first couple steps to condense what you've made into a more digestible package.
If you stumped on how to add some more spice into what you have here, just keep doing what your doing, smashing out whatever emotional response you can from your players ability to go on. You've chosen to give the player 3 lives, but you've never seen someone respond to getting 4 one try and 2 on the next. Vice versa and beyond. I don't think you've considered every decision one make in such a small playbox, something nice and inherent like using the side of the first platform on level 4 to skip the second one, or even feeling enough containment within the small boxed levels to try going left. You should think of a list of interactions that work on a constant, like lives changing, going left on a level, or something absolutely wakey like giving the player one extra shot on a level they get stuck on for a long time but reseting the game on completion. And separate them from things like individual level depth. Consider the constant ones fuel for the player, while the level specific ones work as checkpoints. That way you'll have a good understanding whether players are experiencing the zones of play the way you want them to be.
Here, Imagine you where playing your game, and the jump scare hits you for the first time, even takes a life away from you. Your patient and you wait it out and continue. Your past it and you keep playing the game, it doesn't even scare you off from using the same method. Eventually you get stuck on a level and its taking a lot of trys. all of a sudden the jump scare hits you again its a bit different this time and it takes even longer for it to go away. Rinse repeat, you get pissed and waist all 3 lives against the red wall/jump scare. The colours of the screen change and your on a alternate even more sinister path of levels. I think thats an example of route of reward a player who's going to take the time to complete what you've made is looking for.