Sounds like you're using the Steam Beta Client, which does update very often. Maybe switching back to the stable branch would be better suited for you.
I wouldn't necessarily say that Microsoft dropped the ball here, I'd consider it growing pains. Also to my knowledge this is the first time they actually have a translation layer for 64bit applications.
Additionally, Fortnite and League of Legends require a Kernel-level anti cheat driver to be installed and active for you to be able to play the game. Adobe programs to my knowledge also have some nasty custom copy protection that's always running.
I would not be surprised if the incompatibility stemmed specifically from the anticheat and copy protection drivers, considering that there are no native Windows on ARM builds of those games / programs