I want it yesterday.
I have good news for you! Its there and its GG!
Pro controller support through steam is garbage.
I too have been having issues with controller when I have steam and D2R running. For me I just exit steam while playing though.
Sometimes even still have issues but a quick unplug and connect and good to go! 
Switch Pro controller?
Go to games → add a non-steam game → Diablo 2 Resurrected.
Now right click the game in your library and go to properties. Set the target path to D2R.exe instead of the launcher. As launch arguments, add “-uid osi” and close the window.
Now you can launch the game through steam and take advantage of the builtin controller support.
PS: This bypasses the launcher. Meaning if there’s an update you will have to run the launcher manually as usual.