Reading the report you reference and other issues linked there, I would say that multiple attempts were made to fix it, all of which unfortunately required some heuristics and all of which have broken something else that was deemed worse.
It seems to boil down to an issue in the underlying X11 machinery and it would need to be fixed there first to build a basis on which proper fixes can be implemented.
Given that X11 is in maintenance mode (and as its fans keep saying: It works perfectly fine and doesn't need any more work done on it), it's not likely that's happening.
So, yes, given that information (and I just arrived at that bug report through your post), I would indeed say that waiting for Wayland is the only option they have. All other attempts ended up causing worse issues.
So I guess the "fix" would be to have two completely separate input handlers on X11, one of which supporting smooth scrolling and multitouch, the other not and then offering users a toggle in the style of
[ ] do not ignore the first scroll input after focus loss, but disable smooth scrolling and multitouch
Plus handling all the potential issues by having two separate input handlers.
That's asking a bit much for this particular issue und greatly smells like a case of XKCD 1172
It seems to boil down to an issue in the underlying X11 machinery and it would need to be fixed there first to build a basis on which proper fixes can be implemented.
Given that X11 is in maintenance mode (and as its fans keep saying: It works perfectly fine and doesn't need any more work done on it), it's not likely that's happening.
So, yes, given that information (and I just arrived at that bug report through your post), I would indeed say that waiting for Wayland is the only option they have. All other attempts ended up causing worse issues.