For WvW the expansions are essentially only needed to get access to class skills that are OP compared to the standard class. This can be described as "PAY TO WIN" because you pay for the expansion and you are much more likely to win against a non-expansion class. You can try to argue otherwise, but that is the truth of it.
So let me ask. What do we get as a WvW player when an expansion comes out? I only play WvW or very occasionally PVP. So you can ask the same question about PVP.
I actually paid for the original game. Its free now... But if I were to have not bought the game and supported the company back then and bought it now...I'd have the expansion.
So you are throwing away your base and require money just to stay relevant.
The "upgrades" for the person who already bought the game are really downgrades because all of their characters are now inferior..."but you can pay...um oh yeah...to win.".
So this could be fixed easily by simply turning on expansion classes in WvW. OR making 1 "classic" server. Classic server would be no-desert maps. The water back in the center. Old mechanics. Travelers needed for golems.
Basically back when the game was good.
Lastly the WvW population is almost NONE of the important population we keep being told. That is why it isn't actively supported. So giving free access to class expansions in WvW isn't losing anything is it? You don't want to pay for this? I'll do it for you for free. Sign an NDA and spend a week making the change. If you think it would take longer than that then either:
1.) You need cleaner code.
2.) You need better programmers.
Possibly both...as 2 causes 1 to not occur.