Honestly, what they need to do is make the game better for new players, without making it worse for older players than it already is.

First: an actual, mandatory tutorial that reflects reality on how to play the game. No more going into sastacha not knowing what tank stance is. msq/scenario skips disabled till after tutorial.

Second: return some bumped up job abilities down to the lower levels to make the game more engaging in line with class quests. Add the missing rewards back in (eg: I reached 30 marauder on an alt...what is this butcher's block, where is it? as a veteran i know its deleted but a sprout wouldn't)

Third: lower ilvl limits and capstone based potency boosts. Since every expansion potencies are increased, restoring the old potencies for what they were balanced at would go a long way.

Fourth: lower the exp rate early in the game but have it increased with an invite code item. That way new players on their own won't power level and players invited by friends can catch up

Fifth: make the tank and especially healers less homogenised and with more offensive buttons for healers. Currently you go into the first dungeon with LESS than you had in 2.0, healers especially from level 4 onwards do not get a change in their damage abilities for the whole of the msq- that's a turn off. Imagine if as a blm you onlly got thunder and blizzard for the 80 levels- thats what new players see opening up a healer.