Here’s a good writeup on the phenomenon. It sounds like the big splash was Audi Nardo Grey for the solid, non-metallic high gloss look, starting in 2013. A lot of brands started imitating it, and in my opinion it “jumped the shark” in 2022 when Mini Cooper went big with several different finishes that looked like a 1962 enamel Frigidaire from my grandma’s kitchen (the one with the external latch, which we called the kids’ death chamber, but I digress). Those are the ones I saw everywhere, and they stopped selling them in 2024.
Now if you’re talking about newer more recent finishes, the flat look has evolved toward a more metallic low-gloss sateen. Personally I like these a lot better, though (a) they’re hard to care for since that cool unpolished sateen finish picks up an undesired polish very easily with friction, and (b) something this flashy and trendy will probably get tired very soon now that it’s hit the mainstream market.
So in a few years I expect we’ll be seeing decent used discounts on cars like this that have picked up some undesirable over-polishing that the owner doesn’t want to deal with.