"still missing crucial features such as fractional and consistent scaling"
This has very little to do with Wayland and mostly has to do with the apps and the toolkits. I haven't really seen many Linux native apps that are able to function correctly at a non-integer scale. The rendering of these apps may have to be entirely changed and refactored to use floating point instead of integers. That a big thing to ask every app to do. The hard part is doing that, and then it's trivial to put a flag in Wayland (or XWayland) for an app to say that it supports it.
This has very little to do with Wayland and mostly has to do with the apps and the toolkits. I haven't really seen many Linux native apps that are able to function correctly at a non-integer scale. The rendering of these apps may have to be entirely changed and refactored to use floating point instead of integers. That a big thing to ask every app to do. The hard part is doing that, and then it's trivial to put a flag in Wayland (or XWayland) for an app to say that it supports it.