IANAL but my understanding is that if a cookie is strictly necessary for functionality (such as a login token or storing the region the user explicitly selected) then no consent is needed.

"improve performance and UX using simple analytics" I don't see how performance requires persistent analytics. This smells like a flimsy justification or perhaps "we always did it this way" rather than strict technical necessity. You can send events from a current session without keeping state in the client. And if one truly cared about performance, there's a lot of fat to trim from many commercial webpages that shouldn't require any analytics at all, try opening a profiler first and notice how much time is spent on loading all the analytics stuff.