It depends what they are replacing. Typically, generics used to replace runtime polymorphism (using [T any] []T instead of []any) would be a speed boost in C#, C++, or Rust; and would have no impact on speed in Java.
And it is also a speed boost in Go, assuming you don't call any methods. (Which, if you were really using [T any], you either weren't or you were dissembling about your acceptable types.)
