Code mutation is, in my personal experience, a shit show. With Elixir, you I have to worry about some random process mutating your data because it can't, as it's literally immutable. I have never, not a single time, wished I could mutate a data structure in Elixir, because I can think of no case where it makes my life easier. Even quasi-objects, in the C++/Java OOP sense, like GenServers w/ internal state may appear to be mutating data from the outside, but from the inside they still rely on copying the data to update the state. It's so much easier for me to reason about.
Maybe different things simply appeal to different people. I could make arguments for OOP being harder to scale, but maybe that's just true for how my brain works.