I think the FFXIV problem is that there is no job ability system outside of what you learn from leveling up, which means one of two things is going to happen with more and more levels being added: you are going to have ability bloat from adding new skills every expansion, or you are going to have more of the current problem where jobs get thinned out to prevent bloat which means your job won't feel complete until higher and higher levels which is a disincentive for new players as the gameplay gets more and more stale.