I agree with all the above-mentioned reasons.
But there is maybe another thing that made some people stop playing WvW:
It is supposed to be a 1vs1vs1 competition but many have realised that it, most of the time, turns into a 2vs1 “fight”.
The servers that ally with each other call that “strategy” but it’s in fact a way to be at least twice as much as the third server. Thus they make sure they’ll finish 1st and 2nd weeks after weeks.
But at the same time, players from the third server can’t compete with “equal weapons” and stop wasting their time in this fake 1vs1vs1 competition.