Seems like Reaper is about as modular a DAW as it gets, but because it was built from the ground up to be.
It must be easier for newer DAWs they can take the ideas of Cubase and improve on them from scratch. I do think they should at least begin to add a few more levels of complexity to QControls, but I think priority is in improving the audio/pitch manipulation tools, their chord generation tech, VST/// expression complexity, and incorporating everything into a Halion 5 shell, which is the ‘playground’ to use in Cubase.
That is their bread and butter. And there is a core market for all those features. It makes sense as a professionally geared tool, not so much experimenting with revolutionizing routing, modulation and automation. I think Reaper has a chance to corner that particular market.
It is good that each DAW has specialty, and not become jack all trades. Limitation is very good for art.