I think the most useful high level adventure(s) would be ones built around achieving whatever long term character goals are most common, since many tables would be going into a high level adventure with characters looking at least vaguely towards some sort of retirement. Obviously the ideal option is to create custom content to fit specific PCs, but that's not possible for a prewritten module, so in lieu of that, just aim to check a lot of boxes that might be appealing.
So let's imagine a once great city, under the sway of some sort of evil super-Lich. It has become an unused city of the dead, full of plenty of high level undead. While the outer quarters are still inhabited by oppressed living, because most undead do not require the same things living do the upscale quarter is effectively empty and most institutions have fallen apart. Thus under Mr. Lich's tyrant rule it now has a castle with no lord, a mage tower with no wizard, a magic academy with no archmage, a grand temple with no archpriest, an arena with no star gladiator, a thieves guild just waiting for a thief king, defunct orders of paladins and rangers just begging to be reinstated by the right leaders, abandoned ships at dock waiting for new captains (I don't know why, maybe an undead leviathan stalks the bay), as well as treasures galore, magic items galore, mansions lying empty, and outlying lands with comparable draws for less urban types, etc. etc. And what the heck, the Lich lord also has a magic macguffin that could bring back a character's dead loved ones, the world's most complete spellbook, and has imprisoned a Warlock's patron or a Cleric's god.
Basically just load it up with hooks for high level players to want to go there and free that city and in most cases then semi-retire alongside their buddies as eminent adventurers in their fields and (to whatever degree players care for) leaders or leading citizens of this major fantasy metropolis.
So they quest for a while, eventually confronting and mopping the floor with Mr. Lich. Then settle down and remake the city in their image. There are minor quests to secure necessary reasources (or conquer a neighbor if you've got those sort of players) and also plenty of downtime to achieve whatever the players want the characters to achieve.
But while they enjoy the fruits of their labors, Mr. Lich has been reborn in his real phylactory (not the decoy he tricked them with) and he's out for revenge. A weird little island the PCs had an adventure on earlier is actually all just the back of an ancient sleeping mega-tarasque, and he's going to wake it up and send it to Kaiju stomp their city. And it can only be defeated with the five macguffins of mega-tarasque defeating... etc. etc. etc.
In any case, the details aren't my point, my point is offering an overwhelming menu of inducements to get PCs to go to, redeem from evil, settle down in, and invest in a place, have them fight to do so, and then threaten everything they've gained once they're pinned down.
