What's the point with that quite lackluster story in Endwalker?

[Theodric]

Wait...are you talking about the people who supposedly hate on other players for liking or wanting to side with the Garleans?

Yes - though there is no 'supposedly' in many cases. There's a handful of posters - particularly on the lore forum - who have actively stalked and harassed some of those who have expressed a fondness for the game's antagonists. Usually only in the case of the Ascians and Garleans.

In at least one case, a certain poster uses the exact same name across multiple sites where FFXIV talk occurs and actively tries to police/stalk anyone who...likes the 'wrong' thing in a video game?

As I said, it's all very bizarre to me.