as long as i need to run nvidia with multiple monitors, i'll hang on to x11.
Apart from that, use X11 as long as you wish!
I'm just glad we can finally improve the open source desktop-environment infrastructure to match those of Windows and macOS: we've been stuck for too long.
This is not a problem of X11 itself.
Maybe a years or two until Wayland gets to full feature parity (except for features Wayland specifically does not have like network support and drawing window borders etc.)
In those same two year I expect all app I use to be running native on Wayland as well. (IntelliJ being the main app I'm waiting for and they are making progress)
That's a feature, not a security issue.
Any closed source app could easily contain a keylogger: great feature!
If we want people to run closed source on Linux, we need facilities to sandbox these apps like on other OSes. Flatpak is moving in this direction. Wayland's security also helps.
"was" sure. "still is" it depends on your use case.
for me Wayland overtook X11 as superior in the last year.