[alex7734]

> You could say the same about memory protection and isolation, and yet, here we are.

While it also serves as a security mechanism the most important benefit of memory protection is that it protects against processes *accidentally* corrupting other processes due to mistakes, invalid pointers, etc.

If you want to intentionally mess with other processes memory most OS give you the means to do it in a controlled way, with ptrace in Linux or WriteProcessMemory in Windows, because sometimes it is a useful thing to do.

The problem with Wayland is that they veto useful features they aren't interested in (that admittedly if misused could be a security problem or at least a nuisance) and they don't give any alternative way of doing them, choosing instead to punt the problem downstream to the compositors, who will each do them (or not) in a different way making the whole thing a mess.