POE.Trade became so popular that it going down was toxic to the game.
It has become so popular that GGG basically cloned it and created an official trading site. With a robust and granular search function, you can easily find any piece of gear, Map, or currency item in your area as fast as possible. POE.Trade makes finding items you want to buy, and sell, so much easier. So they design trading less around accessibility and more around being an absolute nightmare.
That’s kind of by-design, as GGG wants the game to be hard, and they view trade as too easy a pathway to power. Without this site, the Path of Exile community would still be stuck on forum threads and the terrible in-game chat. POE.Trade is the trading site that started it all.