The question isn't possible to answer, what one person expects to work another person might not consider it important. Likewise, what does "compatible" mean?

I have used Wayland exclusively for over a year and not found any software I could not run.

For example, JAVA doesn't have native Wayland support, so if you launched GUI JAVA software Wayland will run it in a sandboxed X11 server (XWayland) that behaves mostly like Wayland in the context of the rest of your system but is just X11 under the hood.

However, because that JAVA software is technically running in X11 and X11 doesn't have the level of support as Wayland does for HiDPI then that specific GUI program can't inherit your pixel config. This will probably just mean the default layout for that program will be too small or blurry.

This is a good example because it's not unreasonable that in 2023 you may not be running any GUI JAVA software and you may never even realise this was an thing. Equally, GUI JAVA software may be the only software you run in which case this may be unacceptable.

There are other things Wayland does differently to X11 (because it's different software). For example, Wayland doesn't have a method for a program to register a global hotkey - if you want a global hotkey you have to register it in your WM or DE. This is because the tighter security model stops one program from capturing inputs to another AND because the developers can't come to a consensus on the API to enable this.

You may consider Wayland not supporting arbitrary global hotkeys to be incompatible with what you expect. I don't because I have no issue with the centralised global hotkeys in my WM.

It's not compatible with Talon voice for voice to text. I was going to move to Wayland a year back, but I also had hand issues that meant I needed to use Talon.

Apparently per the Talon developer Wayland makes something like Talon very difficult or impossible to implement? Not sure of specifics.

This gave me the impression that Wayland isn't as friendly with regards to accessibility, but not sure if that's a fair takeway or not.

Nope! I used it for a while and had issues with screen sharing/capture in Firefox and OBS (it did work in Chrome but then my webcam didn't work there - classic Linux).

I never thought it would take 3 decades for Wayland to be mature.

How long ago was this? Screen sharing[0] and capture[1] works fine in wlroots.

  [0]: Supported with workarounds circa 2020, most were merged by 2022 - https://github.com/emersion/xdg-desktop-portal-wlr/wiki/Screencast-Compatibility
  [1]: I've had success using `wf-recorder` https://github.com/ammen99/wf-recorder

Right now. On RHEL 8 admittedly, and it Firefox screen sharing did work at first, but it randomly broke at some point. OBS capture never worked in Wayland for me.