Long story put extremely short with several short notes: The MMORPG community has changed. Mobile devices did a lot of damage in that regard. People are also stupid everywhere. FFXIV is the "Easy WoW," but I like that because I like WoW. If you want to focus super seriously on gameplay as your primary objective, WoW is clearly the better game. For storytelling and awesome gameplay presentation, FFXIV is your game. I have a ton I could say, but it would be an obscenely long post to detail the progression of dungeons & raiding in WoW. I actually did briefly put everything in this post, and I saw it was just going to be a disservice to the thread to make people scroll that much.
To be more specific, from someone that played WoW from nearly the beginning through all of Mists of Pandaria (2014):
WoW has 3 difficulties: Normal, Heroic, Mythic. Normal is something like all three Binding Coils in ARR. Heroic is roughly like Savage raids. Mythic is like Ultimate. Although the raid is the same in each difficulty, the difficulties surely change how it feels. Normal/Heroic are usually the same fight roughly, just different amounts of damage taken. Mythic difficulty, like Savage, completely changes the fight while retaining something of the original. Also, at least when I played, a couple things were exclusive to Mythic difficulty, similar to god Kefka being exclusive to Savage.
I would say WoW's LFR (Looking for Raid) difficulty is like FFXIV's 24-players', but LFR is so much ridiculously easier that that's not fair to say, though both are designed very similarly.
Oh, and I did play Legion, WoW's current era, for a few months when it launched. One really interesting thing they implemented was a Mythic difficulty for dungeons complete with a system where you can challenge a random dungeon on a Mythic+ difficulty that goes up one stage of difficulty for every Mythic+ dungeon you clear, rewarding better gear the higher the stage. The idea was to make somewhat parallel or alternative gameplay to raiding. While I think that'd be cool to see in FFXIV, I don't believe that fits the devs' vision.