Since Shadowbringers, the side quests already give a lot of good xp for little to no effort and they scale up. It was very easy to level up DPS jobs this way.

More XP isn't the solution to everything and they certainly don't need to spend the time going back and tweaking hundreds of quest rewards just because. There's plenty of xp to be earned just for logging in and running content. You've got Hunts, WT, Challenge, Dungeons, Roulettes No one really suffers from a lack of xp unless they're just in here for the wrong reasons.