^ Those two are likely the main reasons why it hasn’t degraded as much in GW2, assuming you’re correct in your statements that is.
For one thing, quick seasons means it fades out a bit. People already don’t need to level and no need to gear in GW2 for PvP, so there’s little preparation needed which means less anticipation and less investment.
Then the fact that the seasons are quick, means that people place less value in each individual season. It becomes more bland. It dulls the emotional investment like that. (An easier to understand example would be to compare a hypothetical weekly tournament with anyone able to join, compared to an invites-only yearly grand tournament. The emotional investment becomes inherently different depending on the “prestige” of it, and its exclusivity.)
Another thing to take notice of is that you said the monthly tournaments only leads to a statue, which I’d assume isn’t really as “grand” as a r1 title with unobtainable cosmetics from past seasons, since according to what you said those kinds of things aren’t limited to seasons, right? Much like the RBG rewards. Which has already proven to not be a strong motivator.
And the punishment system is much more effective, which both WoW pservers and now GW2 assuming you’re correct, shows is a strong motivator to not break the rules.
Meanwhile, in WoW…
Again, what’s with this obsession to compare it to the current design? It’s garbage as well.