Have you played Rainworld yourself? I got it in the fall steam sale, and have been sitting on it. It's installed and ready to go, just a few other things on the list first.
Rain World is a fantastic game but it's admittedly not for everyone. Thankfully since the big DLC dropped last year, the devs added a bunch of options to decrease difficulty and toggle off certain frustration points if it's not clicking with you.
Personally I fucking love Rain World. The creature AI is so immersive and reactive that I would play the game just to go running around hunting and exploring without any objectives. The sprite art is beautiful, the worldbuilding is intriguing and imo the difficulty is manageable, and I'm saying that as someone who sucks at 2D platformers.
Also the previously mentioned DLC adds multiplayer in campaign modes!
