Yeah I know this - I was in the preview thread responding to people who thought that nobody wanted visual customisations so the MTX are pointless. It's a huge part of games like this and it seems like they need to do some work to strike a good balance between what can be earned in game and what can be bought.
Personally, I don't look at someone and think "ooh, they've cleared that content" and when I put my personal design together it'll be because that's the way I want to look regardless of power level. If that stuff happens to come from the high level content then it's a bonus.
I'll never forger having to wear things like this while progressing through King's Fall:
... and would have preferred to have the perks from that on something that I wanted to wear. Frankly anything that stopped me wearing my Helm of Saint-14 in Destiny was abhorrent, whether I needed its perks or not.