It’s baffling when it happens to you, but I will say there have been friends that I have had that I knew for years that I was polite to (and knew well, bc of history & context) that I was cordial to for years after the true “oh I can’t wait to get together and bond” feeling was gone for me out of kindness and shared history.
I ended up feeling like shit about it, but how do you tell an old friend that you feel like every conversation is a marathon and you’re tired of the role you play when you’re with them?
You know those existential conversations go badly…I wasn’t mad, she couldn’t change…I just found the dynamic draining. It’s similar to why becoming an adult and dealing with your family is so exhausting. They can’t get past the 12 year old you, and see a 45 year old adult, and you don’t even remember that 12 year old person completely, because you weren’t fully formed.