I dont care for Ultimates and you dont need to clear them to play the story so I would be fine if they are behind a paywall.
Cosmetics are important to players. A lot of the content is stuffed full with rewards because they know that a lot of it is only done because of these rewards. Most of these rewards are glamour, hair, pets, mounts and now new dye. SE would not sell us so many cosmetic items including mounts if people did not want them. They are (next to the challenge) for a lot of people the reason they farm stuff. So yes they are quite important.
I would be less against the cash shop if there are certain things:
1. Old events items should be cheap. They are basically selling something that was once free ingame for real money. Including stuff that can be eaten. (Yoshida even once said that they are not selling those event items to earn money but to give players a chance to own them...yet the prices tell us something quite different..)
2. Any exclusive cash shop item should be either in the game and buying it would only give it to you faster or there should be a way to exchange ingame currency for cash shop money or sell the items ingame.
Win Win for everyone. Those with income that they want to spend on these digital items can still do it and ignore the grind, the rest can either grind the currency or just the item directly.