This is not sololy a question of amount. Indeed these last months population is scarce. But when you level a character and quest in Khitai instead of just being powerleveld in raids or dungeons you have a pretty great time thanks to that little extra. Compared to the tediousness of it on Crom once you know the quests.
I quest with friends in Khitai, some days, nothing cross our path, some nights some fun squirmishs, and some other nights we can't quest and fight instead. For this, you don't need a huge population at all.
So the question is, do we give Open-World PvP server a chance of a revival after years of undermining them ? Or do we believe it's too late and shut them down already ? I can understand for people that for people who moved to Crom the second option seems better, wiser, why even bother arguing about it ?! But on the other side it's not that simple. Most of the people i play with, don't consider Crom as an option. I want to believe there's more than the few i know !