Sometimes it's okay to use old software, especially if it works well for you.
On Windows I fully rely on StrokeIt, it has been a huge improvement for me which I've used for ~15 years.
Linux's easystroke [0] is now deprecated (and always was mediocre) and the modern alternative "mouse-actions" [1] is not good at all.
I've coded a replacement in Rust+C which works for my simple use-case but it targets X11 and it's unclear for me how I can get low level access to input devices events with Wayland. I've also read something about security getting increased in Wayland so that one does no longer have access to input stuff (unclear to me).
Then the nice thing about X11 is the ability to remotely use a X11 session, which apparently isn't possible with Wayland (except for RDP or VNC which isn't what I need).
You can't as far as I know, the reason it has taken more than a decade to gain adoption is the protocol design turned out to be unusable for desktops (at least, probably other platforms too). I've been avoiding it because Zoom & friends didn't work when I tested them. My understanding of the de-facto situation is that everything sucked for about a decade from the release, then (special mention to Drew DeVault) people started extending the Wayland protocol to cover the original design mistakes.
Documentation is available [0]. If I were trying to understand the state of play for mouse gestures I'd probably start by researching what is going on the wlroots project, that seems to be where a lot of the useful innovation was coming from. The extensions implemented in the compositor look like they matter a lot.
That is a very complex answer. On X, the answer is "grab the relevant window". I can see why Zoom gave the whole mess a pass until the community sort themselves out. I'm doing the same thing; although it looks like (checks) 15 years of patience has been rewarded and Wayland isn't too much of a backslide from X servers.
Unfortunately automating I/O still isn't all that clear, I'd have clicking automated before I move over; it probably is possible but it is just a messy situation to figure out how.
[0] Technically not a Wayland extension, they bypassed the entire system. So now "Wayland compositor" tells us nothing whatsoever about whether the system can take screenshots, but we have to look up compositor-specific support for screencapture. The situation is ... technically better than X, but still silly. They could have avoided years of wasted time by just acknowledging that people want to intercept data as part of the protocol. The situation is a mess and it is silly that we can't have generic Wayland screenshot applications.
The point is, you either implemented a quite complex way to get a screenshot, or just used another implementation as a library. For a screencast, you discover a new here-are-lions land, since you are going to read out VRAM for each frame, with corresponding "speed" and CPU load.
So yes, separate server handles that and more for you. Compositors finally can use overlays (that's how they emulate different scales or resolutions for clients like games, while using native resolution of the display). Pipewire/gstreamer implement a hardware accelerated, zero copy screencasting for you, so you don't have to do it yourself, just call the right portal.
Yes, apps have to change. But they already do change, at least on other platforms. Apple does way more changes in their system, and do you see anyone waiting for several releases until they update? They changed their arch for christ's sake, and except for the long tail, everyone updated within few months. Why it is so difficult on the linux side?
Maybe the reason is not that it is difficult to update, but that the linux users accept crap and apple users don't. Do not accept crap by the proprietary vendors, and they will step up their effort. It's that simple.
If you are talking about screen sharing Zoom, Meet and Slack work fine on Debian stable running Wayland in KDE and Gnome. Teams probably doesn't work on Wayland, but then Teams working on any other platform on a given day is at best a lottery.