I like to feel pulled in to the world i play too sometimes so I get what you are saying. At first when you come from other games from say WoW where there is definitely a theme of sorts and all or at least most the armor fit within said theme. Everything is midevil steam punk high/dark fantasy esk.. you don’t suddenly see 21st centry school outfits.. it is some getting use to here.. Ffxiv seems more relaxed in regards to world building.
If you pay attention though the world of ffxiv is an amalgamation of other universes.. they have access to other dimensions, and worlds. The world also has magic of course that is capable of some serious stuff.. the way i look at it is these glams come from being exposed to other worlds.. In our own real world once someone creates something and the right person sees that creation mimicking starts to happen. All it takes is a glimpse of something that someone else wants that is determined enough to try and make their own. I imagine the same happens in this world.. atmosphere ffxiv is a result of exposure to other worlds and great magics. That is how I choose to look at it.
My glamors are a mix between old gear i just like and a few bits of out of world items. Tho due to my mindset it doesn’t actually break my immersion.. I am still the warrior of Eorzea that can see all and know all with penalty of brief migraines..
You could also just look at it as ffxiv just being pure dumb fun.. nothing stops you from being what you like.
That said i have nothing against a client side toggle of sorts. I think it might even help with the tech drought and people having to use older inferior tech due to high prices and total scarcity of gpus. I mean I probably wouldn’t use it.. but i have already had to reduce the complexity of others glams due to a previous gpu failure and having to revert to an older card. So it’s not like it wouldn’t have practical use in todays climate..