I want to like this game, but I'm not really seeing the appeal.
I do think that the way the character moves around and squishes is very cute and satisfying, and I do think the environments are kind of neat. The gameplay does seem like it could get good: it's got a bit of an addictive nature where you keep pushing down, seeing new environments and obstacles, collecting shiny objects, all while racing away from a consuming darkness.
Unfortunately, it just got really boring really fast for me. The encroaching darkness moves so slowly that it is never a threat, leading to gameplay that has no tension or spice to make quick navigational decisions. The game spent no time in recycling level assets over and over, killing any sense of progression in getting deeper and deeper. Collecting fireflies to break roots made no sense and felt unsatisfying: I'd prefer if maybe fireflies gave you mana to spend on a ground-pound ability to break through roots so the player could have more control and make decisions. Speaking of abilities, the whole 'split apart' ability felt underwhelming: it's got a really lazy animation to it when you reform and all it does is get you past these certain checkpoints and is useless anywhere else. And so on and so forth.
And to top it off, the game has a really boring and unnecessary mobile-game-esque currency to buy skins: I would prefer you make the game itself fun and addicting than relying on number-go-up currency stuff to trick people into getting addicted (sorry, perhaps that's a bit harsh and not the intent, but it's just not my jam).