Is Higher Order Components replace mixins?

Why It’s not recommenced to use mixin any more? It it because it was removed from react 16?

Is Higher Order Components replace mixins?

Is Higher Order Components is the place to write utilities functions which need to be used from a lot of files?

Short answer: yes

Long answer:

Note that higher order components are not a good choice for general utilities,
as these are better written as simple JavaScript classes.

Instead you should use HOC for the specific cases where React related functionality needs to be shared between components