Look, X11's lack of security is real, but I'd bet that most users don't lock down debugging between applications on the system, so anything you could get out of

Look, X11's lack of security is real, but I'd bet that most users don't lock down debugging between applications on the system, so anything you could get out of X11, you can also get out of attaching to other processes as a debugger. X11 allows you to have "network transparency" and run (authenticated) malware attached to your display on a different host and read your keypresses remotely; but Wayland's network scope is limited; waypipe exists, but nobody talks about it, does it work? can you do ssh -something to setup a tunnel and run things and have it just work (at least to the standard of tunneled X)? Taking care of networked malware by ignoring networking for a decade doesn't like not addressing the user needs and then you shouldn't be be surprised when adoption is slow.