The ratings are extremely high for a reason. I'm biased as a first-gen Asian-American with a constantly distracted immigrant mother, but I understand that this is in fact more of a family drama with a science fiction subplot rather than the other way around and I definitely understand the chaos that the film makers were trying to portray. I loved how the directors gave you a sense of the chaos and overwhelming presence that Evelyn was feeling from being aware of her infinite selves across infinite universes all the time, hence the name Everything, Everywhere, All at Once.
I feel like all of the one-star reviews come from people who were experiencing this chaos (and it wasn't for them) and they definitely had the wrong expectations walking into this movie (thinking it's a more convention science fiction with a family drama subplot, but remember Evelyn starts this film being an immigrant laundromat owner). This movie is supposed to be chaotic and overwhelming, that is how multiverse and living with an immigrant mother makes you feel and it’s not for everyone. If you understand the title and the concept, then you could quickly realize this movie isn’t for you. It’s not supposed to be a conventional science fiction like Marvel, it’s supposed to give you the smallest sense of experiencing everything, everywhere, all at once.