It's a very good movie. I am a non markiplier fan who went to the movie because my markiplier fan friend wanted to see it. Holy shit was i glad I went with him, cause this movie is legitimately good.
After having had a week to reflect on it, I think the main problem was markiplier's acting. I think he must be an excellent director and producer, there's no reason he needs to act as well. The movie plays like a 2 hour cut scene in a good way. The bits of world building made me want more, made me want to play the game to seek it out. This was successful both as a stand-alone movie and as an advertisement for the game.
It punches above its budget as well imo. Aside from some janky visuals at the beginning, once you're inside the vehicle with Markiplier, it feels big. It doesn't feel like you are trapped in personal sized submarine the whole time at all.