how do you cut the person closest to you out of your life?

we’ve been each other’s closest friends for about 6 years now, since middle school. they’ve done nothing wrong, we’ve just grown in different directions and i’ve ended up resenting the person that i am around them. i can’t bloom when i’m reusing this same tired soil. i feel miserable and i know they can feel it too. i’ve talked with them countless times about boundaries and what our friendship’s lacking (i have told them before that i won’t want to be friends anymore if x and y doesn’t change), but a certain point i no longer care. they don’t need to change who they are, i don’t need to tolerate feeling stuck. they have their people, i’ll find mine, we’ll be okay if we’re apart. i want to let it go eventually, if not sooner than later.

how would you go about untangling someone from your life who’s rooted so far in? how do you even start? you don’t really need to consider my situation if you have an answer, i just want to hear what others have to say.