I don't think there's a problem with the idols themselves getting brand deals. That's another way for them to make money. It's part of being an idol.
I'd even say K-pop wouldn't be K-pop if it weren't for the numerous ads, magazines, posters, and billboards we see featuring idols. It makes it more fun.
The fans just need to be careful not to get so carried away. It shouldn't be used as a bragging point. It shouldn't be turned into this elitist or classist thing.