Having to go back to a city every time... like you would have to do to retrieve items from your retainers?
I didn't say the system is perfect. It could be improved by making it function outside of cities. But it does some things very well and it makes glamouring far easier than the old system. I'm not white-knighting, I genuinely find it useful for what it currently does - regardless of what additional features could be added to make it better. As soon as I started playing around with it, I was impressed by how much easier it was to keep a consistent appearance for my character while leveling and upgrading gear.
The lack of switching classes doesn't bother me because that's not what I'm using it for. (If it could do so, that might change. But again, we're still in the same situation as if only prisms were available.) I usually raise one or two classes at a time, and if they share gear then I stagger the levels so they don't need it at the same time, or plan an outfit that works for both. That shared outfit is still easier to apply from a plate.
My glamour plates currently have four different outfits for my summoner, three for healers, and the rest are single costumes for classes I'm leveling.
Because I have those costumes all ready to go, I can decide I feel like running a dungeon in my pretty relic gear instead of my usual simpler outfit, switch to it, switch back afterwards. Or change it just to watch a cutscene and see my character wearing that particular outfit.
It means I can glamour jewellery appropriate to each outfit (or invisible), something I wouldn't have bothered with every time I upgraded gear with prisms.
I'm not saying the system is perfect. I'm saying that is has a good use, even if it isn't the one people expected, and saying "it's useless because it doesn't do X" misses the fact that it does Y very well.