Earlier quoted context omitted.
Doesn't wayland take care of many of these concerns?
No, it doesn't. Wayland have some advantages but also some disadvantages, and it isn't yet really mature. Also, wayland, on the sandbox side, doesn't do anything special. As it's just a lot simple than X and does pretty anything except copy a buffer on the screen, it just delegate all IPC and rendering to the compositor, then, in the wayland world, the security issues of X11 are moved on the compositor instead to sta…
( anyway, for sure fix those issues in a compositor is easier and consume less resources than on X11, and then the wayland world is better from this point of view. But i don't think it's yet enough mature, and many WM/DE doesn't yet support it or support it only partially )