Ah, I see! While there is obviously nothing wrong with this kind of playstyle, it does prevent you from taking on some of the... juicier grinds (specially certain grinds that you basically need to solo, which would seem ideal for you to have as an addition to the family-stuff!) - so just to mention them in order to give you an idea so you can decide if (and how much) you're willing to compromisse:
- Astrope (two-seater giant-pegasus-mount) can be earned by completing 2.000 mentor-roulettes - that requires that you have your mentor-status, though. Which in turn requires that you complete all 4 role-quests in Shadowbringers (tank, healer, physical-dps, magic-dps)
- Amaro (Mount) - needs all jobs at level 80
- Pteranodon - Already discussed a bit here, but you'll need all crafters and gatheres at level 80. Leveling them is quick and easy enough, though! And while there usually isnt a strict need to have multiple omnicrafters in the family, this mount (aswell as several titles and some minions) can only be earned by the character doing the crafting
Some things that require less or no compromisse (some have already been mentioned, some might be on your list):
- Fishing: There is tones of stuff that involves fishing. Completing the fishing-log is the most obvious one, but that includes catching the (in)famous "Big Fish" and that can keep you busy for quite a while! There is also a special quest (rewards a title), aswell as the whole Ocean Fishing thing (Mount, minion, several titles)
- PotD/HoH: - if you go solo, you might want to consider a job that isnt dragoon, but one with better self-heals. RDM and to a lesser extend PLD are some of the best picks here. Maybe you have either of those leveled on an alt?
- Sightseeing logs: Those might not keep you busy for months, specially not if you do them with a guide, but they include some tricky jumping-puzzles. If you do the ARR-one without a guide, it could even take you a while to solve the riddles... (I would advice you to at least confirm wether or not your answer is correct before attempting the spot, though - sometimes the time-window is pretty short or spots are only available every two real weeks...)
- Collecting all Triple Triad cards - nothing you can actually "show off", but some of them include nice little lore-bits (I'd recommend using a site like https://arrtripletriad.com/ to keep track of the cards you have)
- you can do something similar with Orchestrion-rolls - there are quite a few of them to collect, scattered all over the place! From being bought with gil or MGP, to being drops from dungeons, raids or trials... make it a rule for yourself not to buy them off the marketboard, pick the one you want to farm next and get to it!
- Going for a relic - if you havent done that already! And I dont mean the Shadowbringers-one (which you should get anyways), but the ARR and HW relics - aswell as SB, if you want to give Eureka a try (full disclosure: I have NO idea how feasible Eureka is atm - it might be dead enough that you dont really stand a chance)
- Hunts - you can always join a Hunt-LS, go on hunt-trains, maybe get that sweet, sweet tiger one day...
- on characters that have a tank leveled, you can go for the specific tank-mounts
- You dont seem to be into PvP; seeing how you excluded that from your list, but for completion-sake: There are several mounts, titles and other items (glamour, orchestrion-scrolls, housing-stuff) locked behind frontline-PvP. You dont need to compete in the actual PvP-liga, just join the fun chaos thats up to 72 people on one map, trying to kill each other!
For most people endgame (besides glamour being the true endgame) will usually be Savage or even Ultimate raiding - you can always dabble with that and see if its for you!