I’ve been using Linux since RedHat 4.2, and for a number of years in the early 2000’s as a desktop. Since then it’s mainly been as a server, and I just recently got back into running it as a primary desktop.
The “it’s always been that way” argument is stupid and you should know better.
ActivityPub is a communication protocol. There’s nothing stopping anyone from implementing it and then adding their own ‘features’.
Just look at how different companies have implemented the HTML ‘standard’. You end up with websites that require specific browsers to run properly. It’s gotten better over the past few years, but god damn anyone old enough to remember what a pain it was designing websites in the 90’s and working around all of Internet Explorer’s shenanigans will tell you it’s not a good time.