I can't think of any rp venues that will exclude you in any way if you're not using mods, especially since all of them are client side. Can't think of any bartender that'll go "ohp laddie yeh ain't got no mare, getcher smart tuckus outta here." As far as paying for mods, yeah some do and its weird. $1,000 in mods though...feels like at that point the person was a whale already, and if they didn't spend it on XIV mods they'd have dumped it on a gacha. Either way, not my cash so I won't judge.

As for raiding plugins, none are needed except ACT. Noclippy is extremely nice for people not parked on the server though, since SE is stubborn about how animations work. Clearly the smartest way to handle ping is to run the animation lock twice, once when client says and once when server says, that won't cause issues for people with >40ms ping! "Fixing this is impossible." -SE.

I don't think the game would die. I think it would choke and sputter out of the big 5, perhaps, especially when not during patch week because a lot of people would vanish between story patches. Square would probably put XIV on maintenance mode eventually after that point, or push the devs to return to a 3 month patch cycle as they see the money printer run out of ink. General player anger at getting locked behind "Soon:tm:" would grow immensely since SE would be directly taking responsible for any and all qol.