It's a simple numbers game.

There are more people playing WoW (yes, even now) - and some have been playing for an incredibly long time.
There is more (accessible) content that requires a group than in FFXIV - so as a player you are naturally going to encounter more people and have some interaction with them.

In my experience there is a higher entry level to WoW than FFXIV - people assume you know what you're doing much sooner than they do in FFXIV and LFR aside, it's a lot more obvious in WoW if you're not pulling your weight.

Overall WoW is more social but demands more of the player - FFXIV is less stressful but doesn't provide the same social experience. WoW is the highest highs but the lowest lows.

Generally though, if someone is popping off on the internet - just ignore it and move on.