But both customization options and gameplay require time and attention of the dev-team. If they put more attention on customization, there is less time for gameplay/new content. Very simple, really. You cant have everything, basically and the team stated several times that their ressources are limited (not only because they might not get enough foundings but also because they actually had trouble to find new, good and qualified people to hire).
Now, I dont play any of those mobile games you're talking about, but as I said before: If those were build with the idea of "Oh, we want to offer people lots of different hairstyles!" in mind their code will reflect that and make it easier to implement this. The code of this game is somewhat of a mess and isnt build around the idea of lots of customization.
But please, tell me: What do those mobile games offer beside customization? Again, without having played any, I would kinda expect a mobile game to lack on aspects that this game is strong(er) in - such as: a good story, general better graphics, different types and amount of content, cutscenes and so on - because those are the things this game focusses on.
Take a look at your f2p-mobile-game and see what FFXIV has that this game doesnt - money and time of dev-teams are always limited.
And as much as I would like more customization-options (and specially no clipping...) I understand that they need to set priotities. And we can ofc agree with those and voice our opinions about what we'd rather see, but we need to be aware that its always gonna be a trade off. If ressources are going one way, they cant go the other one. If your f2p-games says "Hey, our strong side is customization" that most likely means they're lacking something else, that FFXIV might have because the devs considered that more important.
Personally I'll take new armour and a new raid over a butt slider every day - even though I'm playing a Roe who looks a bit ridicolous in some outfits being kinda bulky but with a flat butt...