Movement is there, so is the game idea of going down, surviving etc.
But this thing is barelly a template void of any objective besides the skin unlock, which would be horrendous to grind for, since the game in its current state lacks a motivator.
Below is my take on this.

Toggleable sidegrades either as suits or as simply buyable and toggleable things (the latter would allow for free suit customisation)
Examples:
Less fall damage, but higher health drop
More fall damage, but lower health drop (Marsonaut would fit, if you choose suits as the upgrade thingies)
High jump, but jumps consume energy.
And so on.

That way you keep this game as it is whilst giving players choice and the grind a meaning.

don't want to sound too harsh, but its kind of boring and lifeless
needs some music to liven it up really
as for the gameplay itself, it's a decent enough concept, you just have to work on the execution a bit better
like, for example, it would be better to have time remaining separate from player health

anyway, i think with some work you could make this pretty playable ;)
- jack

i like it,you should add a bgm to make the game better

Honestly, this feels like an alpha. If you're trying to make something like Downwell, you gotta put a bit more effort in than this. For one, you literally die from fall damage, making risky or exciting play basically impossible. Second, enemies are just boring. 3. Player has great speed but once he becomes too fast it becomes impossible to control basically. Because you can't see what's happening. I'd like the speed if it allowed me to react or do something with it, like imagine smashing through enemies or what not.
4, final note. The player doesn't really do anything more. Maybe mid air jumps, or weapons, or something. The gameplay needs some variety.

Anyway, while my criticism is harsh, I do see what you said about this being a Gamejam game. Don't give up, take up that criticism and make the game more exciting.