This, right, here.
I'm also a long time WoW vet, not playing quite at your rating, usually in the 2300-2400 range and on US server, but I felt the same exact issue that you did. Looking at ladders is very misleading because of no decay.
Yes, downstate sucks. I think very few people could come up with a decent argument as to why downstate is better than a non-downstate system, but you can't say other games PvP modes are thriving so much compared to GW2's, because they really aren't.
The real issue, IMO, is that the vast majority of people that play MMOs play for the PvE. WoW and FFXIV are the two biggest because they easily have the best PvE endgame of any game out right now, I don't think there's a game that even comes close. Once players realize games like GW2, BDO, ESO, etc. have very lackluster PvE endgame, they leave for games that put more focus on it.
And these games seem so much more active and populated because of the huge PvE playerbase, which isn't inaccurate, but if you're playing an MMO for PvP, which I imagine most of us still playing GW2 are, the active playerbases in the PvP scene are probably not too far off from each other.