While it is certainly possible to play your favorite FPS games by connecting a keyboard and mouse on your console, that can still have some complications - at least if you're an Xbox console player.
Xbox console players are experiencing an irritating error when playing with a keyboard and mouse. The error pops up saying, 'You need a controller for this game,' with a huge pop-up on the screen interrupting the game in the middle. This can be frustrating if you're playing online games such as Apex Legends.
Apparently, the error is quite old, and many are experiencing it recently, probably due to a surge in keyboard & mouse players on Xbox consoles. This was indicated as a user name SlamDeath36 posted a picture of them experiencing the same error due to the exact same reason back in November of 2021 on an Xbox forum.
With Microsoft's acquisition of Activision and new Xbox Game Pass announcements, it won't be a surprise if PC players are buying Xbox consoles to reap the benefits. Hence, the recent rise in popularity of this ancient error.