What you’re saying is probably valid for a desktop (especially if it doesn’t use Nvidia), but laptops (especially Nvidia ones) are still far from perfect. Personal experience with Ubuntu on a recent Thinkpad:
* When using Wayland, until VERY recently (latest nvidia drivers), the entire system would freeze when hooking up an external monitor. Okay, no problem I’ll use X.
* Hygrid graphics just completely doesn’t work, loads of glitches, glacially slow framerates on external monitors, etc. Okay, I turn off hybrid graphics in the BIOS, but that absolutely trashes battery life.
* X does not let you run different scale factors concurrently. You can’t set your laptop screen to 2x and your external monitor to 1x. Wayland does let you, but see above.
* I have two 4K monitors hooked up to my laptop. Whenever I resume from sleep, there’s a very good chance that only one or zero of the monitors is detected. They both power on, but only one (or sometimes none) of them actually has a signal. Cycling power on the monitor usually fixes the issue. My coworker has a Thinkpad from the same line but a generation earlier, and it had the exact same problem, so this has apparently been around a while and still isn’t fixed.