This is a misconception that you pay your subscription for the patch content. The patch content is incluced with the base game and expansions. When you buy the Endwalker expansion all future patches of that expansion are already included in the price of the expansion.

You don't had to pay a sub while a patch released to get access to the content of that patch later on.

So the literal answer to "What are you paying a subscription for?" is:

You pay to get access to the game. Everything else you have to pay extra for. (And without paying the sub you will lose access to that extra stuff which you have already payed for)

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Well me personally I have a small FC with people I like a lot, I enjoy grinding stuff and especially fishing. I am doing Eureka again, have still things to do in Bozja, have a handfull of rare fish to catch, have to finish Eureka Orthos, crafter relics from ShB and EW, fates, leveling jobs, doing Diadem for the Pteranodon, clearing ShB ex trials for the mounts...

The list goes on and on.

Sure I am unsatisfied as well mostly because of the poor execution of the relic quest and the lack of incentive to do Criterion Dungeons - which I also have to finish still.

But even after 26k hours logged in the game, I am far from running out of content.