Closest thing I can think of to that would be Destiny 2.

Normal Strikes and patrols in the open world you can shake off most incoming damage easily and leap about all over the place if you so desire.

Something looser like Borderlands 2 but cranked up and with crazier guns sounds fun though. There was a MOD for UT2K4 called Fraghouse or something like that that scratched that sort of itch for me way back. Install monster packs and run around like a lunatic killing waves of ridiculous creatures with redonkulous guns .