The only player here who is salty is the FFXIV 1.0 player. This game was initially based on an original concept. Now they're patting themselves on the back for becoming 'more like WoW'. I'm not certain why you would think WoW players would be upset by this.
Eh, I hate to say this but 1.0 sucked. There was pretty much nothing good about it that I could see when I tested it back during beta. It was archaic, the engine did not work very well whatsoever, and the UI was just entirely horrible. I've also seen video clips of later-game footage, such as the Garuda fight and... yay, the tank is standing there for 20+ seconds auto-attacking... that's... "awesome" gameplay, innit? Kinda like FFXI all over again... no, thanks. If I wanted FFXI, I'd log into FFXI (which I still do).
Becoming "more like WoW' was a huge improvement that I think many players would agree upon (hence why ARR is far more popular and well-received).
Many WoW players, on the other hand, are incredibly jealous about their game. You see it on forums, they get vehemently defensive about WoW is "THE BEST!" but yet these days... WoW really isn't the best and they are having to reach further and further to try to defend the mess that is WoW these days. The avid WoW player wants to defend his game, but is finding it harder to do so when FFXIV just keeps getting better.
He doesn't want to have to eat crow and admit that WoW is no longer the best and that FFXIV is better.
That's why some WoW players are probably getting salty at this point, at least the avid fanbois anyways.
There is no inverse relationship between these games. One doesn't get better as the other gets worse. XIV put themselves in more direct competition with WoW, but that's smart from a business aspect(if you ignore it's impact on FFXI). Competition is good for both business and consumers*,
I wouldn't say FFXIV "competes" with WoW when Yoshida himself said that he wants FFXIV players to play other games too, lol. His team designed FFXIV to be a more casual game that leaves you time to play other stuff which is one of the reasons why (at least for me) FFXIV is far better than most other MMOs. I can maintain an active sub in FFXIV and if I want more time in it, there's stuff for me to do but if I don't feel like playing it for a few days, no big deal I can catch up later. I'll binge on XIV for awhile, and then take a break from it for a few days to do something else a couple weeks later. I like to rotate my games, keeps things fresh.
EDIT: Full disclaimer: I used to be an "avid" WoW player. There was a time I once played it for 25+ hours per week. I used to love WoW, but I gotta admit... they ruined the game, turned it into a hot mess. It was so sad to see the decline, but oh well. It is what it is. I'm just thankful that XIV is here to step up to the plate and provide me with many of the things I enjoyed about WoW, without the things I hated (like World PvP). Edited, Aug 27th 2017 7:41pm by Lyrailis