Mutation (or not) is a matter of runtime semantics, not surface semantics. Let the compiler figure it out. (Functional-but-in-place c.f. Koka, Roc, Lean4)
Purity and referential transparency make writing correct, zero-maintenance code easy.
Although you can extract a lot of money from your customers if you deliver inscrutible code that needs a lot of maintenance.
Modern OOP is an antipattern.
I try to only write in easy language if I can. My favorite one is Lean4.
There’s lots of this vs that discussion in this thread. IMO the most useful such distinction I’ve encountered is languages that encourage you to think about data vs languages that encourage you to think about transformations (of data). Excel and modern OOP are the former while haskell and digital signal processing are the latter.
Harmful: compilers
Better alternative: magnetized needle and a steady hand