The biggest thing I can think of is that X11 is more flexible when it comes to specifying custom resolutions; which some people use to output 240p on CRT TVs for emulation. AFAIK, there is currently no real equivalent for xrandr on any Wayland compositor.
I’ve also noticed that Grsync’s password prompt is broken on Wayland. Thankfully, it has a feature that lets you preview the command it’s about to run, so that you can copy and paste it into a terminal.
Being a KDE user on EndeavourOS, I use Wayland everyday. I switched over a few years ago for Waydroid, but now X11 isn’t even an option for me with the current release of KDE.
So, just discovering the joys of virtual monitors available in the kernel now. NAS now has and gives me sunshine. Bazzite lets you put your own monitors’ (ujust setup-sunshine - Configure Virtual Monitor) edid into initramfs so sunshine (and KDE remote access if you want laggy but cut and paste enabled) work without a monitor connection (or dongle), very cool. Just thought I should spread the news and this is vaguely associated.
Not really relevant to the X11 question, except that it provides a (superior) workaround for some issues…
To the actual question, xtool for automating UI stuff hasn’t been completely replicated, but given it’s an insecure horrible solution I’m OK. Also running a program through a remote connection on a beefier machine was useful at times, is there an equivalent other than remote access?