Endgame players are like that big fat chick in the nest, shouting the loudest for food. You then spend hundreds of hours on this new content and they burn through it in months and start shouting again for more. This is not new, this happens on every mmorpg from everquest to wow.
I'm well aware how important endgame players are, for many reasons including aspirationally to everyone else and for the economy but they are still the minority and some more thought needs to be given to casual players too.
I'm not asking for whole new types of content aimed at casual players and starving serious endgame players, I'm asking to put casual content that already exists in the rotation for minor updates instead of being considered complete and never updated again.
Why not add some new pets to the mog garden rearing system with new cheers, you don't need new baby models just scale normal models down (we will understand you can't make new models for babies at this point..). This is not hard to do and this would be a great addition. Why not add a 2nd bay area so players can raise 4 other pets instead of the current max of 4? You could even add a hidden area to put pets into rest (storage for fully raised pets, that so you can own more than the current 4 max)
Update the kinds of harvests from gardening, make it worth while (add clusters for a start instead of just single crystals, add other things that make it worth doing again).
Update chocobo racing, add buffs to any mount for doing the content (speed buffs or regen to all mounts)
Add more rare ex crafts to crafting to make it worth skilling up for more casual players that may never take them above 70.
Why not add a few new monsters to monstrosity?
These do not take a lot of work to update but would add a lot to the game for more casual players to enjoy, pet rearing alone would be a big deal for a lot of players and offer long-term interest.
One of my biggest gripes with FFXI is a lot of content people like never gets updated again after and is seen as "complete". Why is gardening never updated at all, why is chocobo racing never updated at all, why is there never small tweeks for abyssea, small additions to gardening, new additions to pet rearing...the list goes on.
Start putting minor updates to old content, this is big payoff for small amounts of work.
FFXI has always been that game with a mass of different things to do, if you never update the mass of things though it just turns into "this is the new themepark ride and that's it!"