When I finish MSQ, I have the following to do:
gathering
crafting
roulettes
FATEs
Hunts
Raids and trials (synced or unsynced)
PvP (I don't touch it but it's an option)
PotD/HoH
relic grinds (I'll include Eureka/Bozja here)
leveling alt jobs
housing decoration
gardening
Island Sanctuary
farming items for glamour
achievements if there are rewards I want from them
tribal quests
side quests
Treasure maps
Gold Saucer
Probably some other things I can't think of off the top of my head.
The game is filled with content to do after you reach level cap, or really any time at all once you hit the appropriate level threshold for the content. You not being interested in doing that content doesn't mean it doesn't exist.
If you're coming back just for the MSQ, you could save yourself a lot of money by waiting for the x.3 patch (which usually wraps up the latest story arc, 6.3 being an exception), sub for a month or two, do all the MSQ since the last x.3 patch then unsub again until the next x.3 patch.
Or keep paying just for the forum access if you want. The forum here really isn't much of an echo chamber. Most threads have their dissenters as much as they have their supporters and posters will frequently change between the two sides depending on the topic. The main problem would be the people who come in here convinced that everyone hates the state of the game or hates a specific portion of game design, and then resort to the ad hominem attacks (like "white knight") trying to discredit those who are still enjoying whatever it is rather than admit it's possible for others to have different opinions.
If there are parts of the game you are still enjoying, like MSQ, then great. Keep paying to participate in them. Unsub once that content is consumed then wait until sufficient new content is released to make it worth the resub.
But considering the tone of your posts, I'm finding it hard to believe that there is anything you're truly enjoying especially when you make statements like "I've been conditioned to stay subbed because of the housing system," That makes it sound like you really don't want to be here.
People might dislike being told "if you're not having fun here, play a different game" but it's good advice being given for their benefit. It makes no sense to stay in a place where you are not happy, especially when you have to keep spending money to stay. It's far better to find what makes you happy than spend your time and money on something that leaves you unhappy.
