I'unno man, some of those myth critters do a pretty good job of blasted hellscape, from what I recall. Usually not planet wide stuff, so it's still a possible step down from a sauron victory route, but... still.
Sometimes they can be good or bad depending on how you treat it, sometimes they depopulate a nation because sod everything in it, it's in the way or summat.
Lot more didn't go the localized disaster route and "just" had a diet of human (parts) or somethin', too. Plenty of times they're capricious as all hell and whether or not you walk away on foot, crawling, or in something's stomach is effectively an RNG check. Roll whatever diplo number you feel the DC ain't a persuasion or etiquette check bub, shoulda' used that cha as a dump stat. You had your be polite ones and you had your run the hell away and pray you fall off a cliff or somethin' instead of get caught.
Basically y'might be underselling what "just live with it" would probably mean, heh. I'm not entirely sure a environment where those critters were actually around and active, as opposed to stories and the occasional event attributed to 'em, would be much more livable for humans than a mordor world tour. Lot of ways you'd basically be taking much of the many, many ills of mankind in the olden times and personifying the bunch of 'em. It's one thing where folks
think they're real and a rather different one when they're physically walking down the street, ha.
There may indeed end up a with a lot more
stuff still living, though. I'm just not entirely sure how much of it would be humans