There are a ton of long standing security issues. Which is why they are working on wayland: X11 isn't possible to secure as bad security is part of how it works.
My desktop is not a smartphone where I download random shady apps from an app store. I don't need any of the "security" wayland offers. If I don't trust some software I simply won't apt install it.
You are not the only user.
I am the other user like him. Where are your imaginary users?