RDP itself in its earliest versions is just a windows GDI async RPC. Which is why its so fantastically fast/responsive on windows. And as of last time I mess with this, thats the way it still behaves for things like MS office, and basically anything that is older than a half dozen years or so, because they are still sitting on the win32 GDI.

But, yes your right if you have a "modern" application that is basically doing all the drawing on the CPU to a generic canvas with custom libraries none of that works, and RDP has to fall back to diffing and compressing. Which is really terrible on any number of fronts.

At that point you might as well just use VNC because the perf is going to be roughly the same.