any other MP games that expanded their loot pool as much as MEA?

I don't remember any. The games I played have usually "zones" where specific loot drops. Or they have RNG for materials to use for recipes.

Actually, there is Elite Elite Dangerous - it has RNG for materials in RNG zones and RNG encounters for an RNG outcome on your recipe. THAT is worse than Andromeda. On feature release there was an incredible bloat of these RNG mats. The whole system is stupid as fuck - but what's even more stupid is that the recipes allow super OP equipment that can trivialse the gameplay - and it's MP, too. It ruined the game for me.

The bloat in MEA didn't ruin it for me. I think. It's the gameplay that just doesn't really cut it. Or do I just have had enough of horde mode? I'm not sure. Gunplay isn't fun at all in Andromeda for me. Power play wasn't fun when it released. The dogs aren't fun. Bulletsponge isn't fun. Reloads aren't fun. Double Berserkers aren't fun. No Krogan running melee isn't fun. And there is no Justicar.

Yup, Diablo 3 has made it easier and easier over the years to actually get the items you want, with Smart Loot first, then Kadala gambling, then Kanai's Cube receipes. I mean, I guess you could say the RMAH was easier than that since you could literally buy the item you want, but they destroyed the in-game loot and itemization to allow the RMAH to exist.

Ah, yes... warframe. The game that makes you go "What's this weird purple thing growing on my neck?"