AFK players are a known issue since Destiny 2 "The Curse of Osiris" for what I can remember, when many players used to AFK in PvP just to get the Mile Stone.
But I'm afraid there is no much one can do about it. I've never heard of a system that can recognize an AFK player or a Player that just does nothing of concrete during an Activity.
Being kicked for inactivity is a thing. Plenty of games have it.
Hell they use it in destiny. If you stand around in the tower not moving it returns you to orbit.
For some reason it doesnt happen in pvp though.
Yeah, of course, and Destiny has it too, also for Gambit and PvP. But it doesn't work if you jump once in while or simply go around moving a little, that's what I mean. And that's why many players can AFK some Activities... like, for example, they can simply stand close to the PS4 watching a movie on the PC and now and then click the jump button to avoid to been kicked.