This is not completely correct. While yeah the devs (actually the higher ups employing the devs but lets just go with devs for simplicity) have final say in what is being implemented into a game or in which direction development goes. But games are not created in a vacuum. (Focus group testing etc)
But for mmos or similar live service games the playerbase is a very important factor in deciding a direction for the game.
Savage raids were not implemented solely because the devs wanted it but because there was a demand for it. The split between different difficulties in a content are direct answer to what the community wanted at the time. 24 man raids are also a good example of that and their flux of different mechanics and difficulty.
So I fully believe if there would be a sudden outcry by a great majority of the player base to have a greater focus on PvP Square Enix would shift their development in that direction. BUT!
This is highly improbable. Given that the focus on PvE and story over the course of the last decade and an ever growing success with each expansion. And yes each expansion was more successful than the last is a clear sign for SE that they're going in the right direction.
So certain core values have been adopted by the community with these core values expectations are set in place. Going against those expectation just for the sake of "shaking things up" would be too much of a gamble for almost any developer. ESPECIALLY SE after the ordeal they went through between 1.0 and Realm Reborn. The team is all about transparency and a 180 turn like shifting this game from PvE to PvP would not happen without a serious dialogue with the community.
And there is pvp in the game. The lack of meaningful development of those modes except the occasional updates shows that they're not FF14's most popular past time.
Nothing out of the ordinary PvP gets updates every now and then. Because they recognize there are fans of PvP in the game but they're not the majority.