As I mentioned up-thread, I've run three campaigns that reached high-levels. Based on that experience, I don't think adventures are really the best way to support that level of play. In all three of those campaigns, the trajectory of the campaign at high-level became very much intertwined with the player characters. Their back-stories, their goals, their abilities all shaped the direction of the overall story heavily.
Sure, there were world-shaping (and multiverse-shaping) events taking place that the PCs needed to deal with that would have been the same for any group, but many of the adventures along the way would have unfolded completely differently if, say, the group's main spellcaster had been an illusionist, instead of a wizard with an increasingly unhealthy belief that necromancy was the only viable way to build an army large enough to defeat the mind flayer incursion. The campaign became the story of the PCs coming into their high-level powers and using those to deal with the threats facing the world. For the players to feel that they have real agency in the campaign setting, past a certain point, who their characters are has to determine how the campaign unfolds.
I guess a well-written adventure could still provide a decent framework for high-level play, but my experience leads me to think that a toolbox of monsters, locations, themes and DM advice would be of a lot more practical use in play. And yes, I realise that that's not dissimilar to what the Epic Level Handbook tried to do, but that was also weighed down by a lot of unnecessarily crunch.