I guess the meme is because Uniqlo is cheap as fuck there that one have to be so poor to not be able to afford it. But ironically in my country, it's quite a prestige brand because my currency is even weaker so it's actually quite expensive.

The meme is about the inflation.

Uniqlo was cheap as fuck. Now it's gotten so expensive that even median Japanese can't afford it.

I wouldn't go that far. Sure, it's not as cheap as it used to be, but the average Japanese person can certainly afford to shop there.

As always with the memes, I agree that it's largely an exaggeration. But I can assure you that it is definitely getting too expensive these days, and I'll think twice before buying from them.