I don't really know the details of this but for some things it is non-trivial to ship even small changes on other platforms, even those will have to go through full dev-test cycles which takes time and money. About removing things, I don't know, I had a car once that had some really nice cupholders. Really deep and exactly the right size, exactly at the right height for the arm. My current car doesn't have them and I can't find any cars that have that were quite as good as that. They just stopped making them. If that's not "vision" then what is it? I mean somebody has to make the decision of how to make the new cars. There is also the question of, do I value cupholders over everything else in the car? Would I buy a car with terrible steering if it meant the good cupholders? If I could get the good cupholders in any car would I pay an extra $3000 or however much the dealership charges? I think probably not but it really depends. So there's many factors at play here.

Edit: Or say maybe I am a startup founder and I design and build my own car exactly how I want and turn it into a company. It's perfect for me but then someday I get bored of driving my car and I retire. Then I hire someone else to design the cars and pass responsibility on to them and they change some stuff. Well, now the cars are different and everyone pretty much has to accept it because the original designer is gone, and as much as people liked the old one, nobody else can really copy them exactly because it was really their personal vision that made it what it was.

For Wayland, I think all of that is happening already? There is somebody making an implementation in Rust. They did try to make a shared implementation (Weston) but it turned out that people didn't actually want that, they preferred to write their own implementations.