There isn't that much free content when it comes to customizations, specifically outfits, clothes. Not much that is earnable (nameplates technically fit, but not fully).
There are a lot of people who can't properly make a character that represents themselves unless they spend money. Which is where some people feel really saddened and disappointed with, along with not having anything that's visual to earn. (Again, nameplates technically fit, but not completely. It's at least a step in that direction).
I know people say plushies technically are, but that's on your plot. most people are referring to skill outfits, for example. (Level a skill enough, unlock a piece of clothing, etc).
And some of it might not feel optional for some folks, since like above, they want a character that might represent themselves. So it really blows. Landscapes also kinda teeter that line, considering some might buy them so their plot has a specific "vibe" (esp for house tours. This is at least debateable).
I also wish there were earnable outfits/cosmetics like that, bc then it'd open up for me to make new alt accounts to have my own ""roleplay"" character, or build a character backstory. I dont' feel like I can do that how I'd like, due to the lack of cosmetics in that regard.
And I want to note/clarify: Nobody is saying there shouldn't be premium cosmetics or a premium shop. People usually want a balance on both sides, and that seems to be very lacking for quite a handful of folks, myself included.