I think the problem is strictly because of how our release works.
In KR, the last ilv gate was like 6 months ago. People have had their main past the max ilv needed for any content for a while, and have had time to push alts up and swap mains if they want. If a new class came out they could put all their resources into it and lose no overall progress, and swap to it as a main.
With how our version works, you’re basically locked in to your original main unless you want to fall behind in ilv and progression on things like relic sets, and with 1415/1445 Valtan on the horizon there’s no way you’re going to get a new class anywhere near that in time unless you are a whale, so there isn’t much motivition to use Glaivier as anything but another alt to funnel your main.
Most people don’t find that exciting or motivating to play.
Unfortunately, AGS/SG don’t seem to want to boost people up the the ilv of the new content and instead give us events boosting people to the start of T3, several months away from Valtan. And then of course they say they have to delay content because people aren’t high enough ilv.