Theoretically Xorg can be made fully secure: just isolate clients so they can only receive events and bitmap information from windows created on the same client connection. It would be relatively straightforward, if quite involved, to implement.

But nobody wants to implement it because everyone qualified to do so has jumped ship to Wayland. The X architecture is so fatally flawed that the most straightforward way to fix it is to start from scratch, and that's what Wayland is.

X is like global warming: one hundred percent of the people who are in the least wise knowledgeable agree that it is a problem. Unlike global warming, however, that problem has a fix: Wayland.

So just... shut up with the irrelevant bullshit and use Wayland, like all the Linux graphics maintainers and distro maintainers want you to do and have been telling you to do for years now... or find your shit unsupported.