People call it open world exhaustion, but it's a bad term. Look at Disco Elysium. It's an open world game, but nobody is complaining about it. So what people are tired of are... ubisoft games. Games that are chock full of paltry and busywork things that keep you playing but provide no real enjoyment. Unfortunately they are also incredibly good at keeping players "engaged" as humans like clearing things off a list and completing small, manageable tasks.
And with every damn AAA game having wet dreams of being a world hit P2P live service trash, I don't see it going away. Also halo is now open world game with map markers, so don't get your hopes up.