ending a friendship

adults well into their middle years should be able to articulate why they no longer wish to communicate with people they once sought out for companionship/conversation

But, like, why would you want to hurt somebody if you didn't need to? Obviously if the person notices that you're ghosting and asks you specifically then the adult thing to do is to let them know, but most people don't really notice a cooling off. If you're messaging/calling/arranging to see them just to tell them that there is an aspect of their personality that you don't like and for that reason you would rather not be friends any more, that's not adult and responsible behaviour, that's just cruelty.

"Hey Bob, sorry I haven't seen you much recently, I've decided to prioritise my friends who don't do that embarrassing slurpy thing when they eat. Bye forever."

Completely otm imo

never realised how unusual it was to not do friendship accounting/try to optimise social relations

not sure "abusive behavior" is necessarily accurate in all cases when they just might not be a great friend
I mean, if I did something genuinely irritating or socially abusive it'd be good to be clued in
I don't need a call or letter from someone when they decide to stop being my friend because I rebuke their political rants.