IMHO a lot of sets look cool. And some paid look meh.

I don't mind the paid cosmetics or the store at all. There is some really hilarious stuff in there... (ring a bell emote? :D )
But I feel no urge to spend any money on that. As you said, I paid the full price as well and see no need for support (yet) as in PoE.

By level 58 you should have plenty of transmogs unlocked, perhaps try a few similar named armor pieces to create a streamlined look and play a bit with the color palette.
Sorry to say, but I do not like the druid cosmetics at all. Other classes have way cooler items in comparison.

With seasons there will be more cosmetics to be unlocked with the pass/season journeys, so there is much to be unlocked over time.

58 druid here as well, I love armor in this game so much. The pieces often fit together quite nicely by default and if not, you can easily transmog/recolor and get a really impresive look. That's why I haven't even checked the shop yet, what's the need? Usually in RPG games, at the beginning you look like a hobo who found a full dumpster of clothes next to a circus, only with time you get cooler looking stuff. In D4 you start cool and only get cooler. I love all my furs, staffs, totems, gloves, everything looks so well.

MTX in a $70 game with paid expansions is 100% BS.

The cost of the paid sets is so much more expensive than I'd remotely be willing to pay that I don't know why they're there. Like basic new cosmetics that can only be used by one class are a minimum of like £20.

I'm finding the general options available pretty good tbh, though I wish that Druid in particular has a slightly more diverse set of options. Would love a slightly more plate look

I am very against the comsetics, just because of the cost of the base game.

That being said, if the cosmetics were way cheaper (max $5 for a full set), I might consider some of them. There is at least one for the Barb that I like, but due to how zoomed out the game is, it really doesn't ever make sense to buy cosmetics at any price.

They aren't going after the average player for the cosmetics, they are going for whales and people with no impulse control.