I think saying the majority of art assets will be in the store is not accurate.
I just look at it as the alternative being f2p or b2p. Both of these payment models pretty much necessitate a pay2win cash shop that a sub allows devs to avoid. Instead they can concentrate on making a challenging, fun, immersive mmo. Not trying to 'persuade' players to partake in the cash shop. But if you want those extra cosmetics and have some money, I don't have a problem with extra money pumped into the game to make it even better.
But if you have concerns, I'd suggest getting involved in the forums. You can use the link in my signature (and gain my appreciation
. Also, the discord is very active and has a ton of useful information. Channels with ask/answers, pinned messages with a lot of info. Steven is there talking and answering from time to time as well.