If you start at 1/15/20 without MSQ, what are you going to do to level? Let's take PotD out of the equation, since that's a point of contention as you really don't "learn" your classes in there.

You're going to do FATEs. You're going to go into whatever dungeon is of your level 100 times.

Guess what?

FATEs sync you. Dungeons sync you. There is absolutely nothing stopping you from grinding a bunch of level 25 fates for three hours or running Haukke 24 times synced. You can still play exactly how you would to begin with, you can even remove all those annoying skills you won't have access to at that level anyway.

And best of all, those of us who don't fancy yet another mindless grind with the same 3, 6, 7 buttons for a week don't have to do it, which doesn't affect those who want to in the slightest.