> "broken by design" is an extraordinary claim and requires extraordinary evidences
There are many technical aspects that make Wayland broken by design (like default forced vsync, forced double buffering, a fucked up event-loop for single threaded applications or severely lacking functionality for things like window positioning or screen sharing). But the biggest problem is the design-philosophy: Wayland makes life extremely easy for gate keeping "Protocol Designers" and extremely hard for application developers.
> un-sandboxable
Not true. The quick and dirty way would be using Xephyr. Besides that many access control hooks like XACE are present and standardized in the X11 protocol for many years. Application developers just choose not to use them. So if X11 is not secure enough for you, blame GNOME and KDE, not X11.
> like default forced vsync, forced double buffering,
A few things:
1. Vsync-by-default is the norm. X11 was the outlier.
2. Wayland does triple buffering, not double buffering.
>a fucked up event-loop for single threaded applications
I dunno, I wrote Wayland applications and I did not notice any peculiarities w.r.t. the event loop, at least in comparison with other platforms like Win32.
You need to expand a little more.
>window positioning
I suggest to read up on the Gitlab MR for the in-development window positioning protocol. The basic TL;DR is that window positioning has certain implications regarding tiling window managers and other unusual desktop usecases e.g. VR.
>screen sharing
I just shared my screen this morning.
> Not true. The quick and dirty way would be using Xephyr.
...So what you are saying is that you'd need a separate server running. Thanks for telling me that X11 is unsandboxable.
Now, X11 being un-sandboxable is truly something broken by design.