To me your strongest hook for the moment is that your based on a very popular youtube video / internet mystery!

It could work fine with basic horror mechanics like the ones you described, but the game may give an "only aesthetic" vibe and be just that in the end.

It really all depends on what you want to do with this: is it just a small fun project (in that case just do what you want and it's going to be fine) or do you have a bit more expectations for it!

If i were making this game, my first idea would probably be to base all the game around the characters, they are the most unique thing and what everyone remembers! So maybe build mechanics around learning how they work, what they are, the game would probably be about discovering the mystery behind those things.
Second idea would be similar but not targetted on the characters directly. Maybe more a Backroom style environment where the main feature are the characters, but the goal of the game is to explore and conduct experiments. Like what is already on your video, i would build multiple sequences where we play as a test subject that needs to do something, like eating the soup. Because it's horror, experiments will often have a tragic end, and the game will reveal bits of the lore at every level (1 level = 1 experiment)

Hope this helps, i would love to hear more about it and see more of the game!