To be fair to the poster you are responding to, this old grognard finds it a lot more work to prep the current adventure hardbacks than the old modules, and not just because of the number of pages. I loved running Curse of Strahd, but it took a LOT of homework to prepare it and I relied heavily on a number of aid to keep things straight in the game (some excellent outlines on DM's Guild, DnD Beyond for text search, etc.). Dragon Heist, Storm Kings Thunder are the same. I have not bought Princes of the Apocalypse, Out of the Abys, Tyranny of Dragons, or Hoard of the Dragon Queen but they seem like a similar chore. I find it much easier to run Tales from the Yawning Portal and am looking forward to Ghosts of Saltmarsh. I also have a new appreciation for the other classics having bought the first two Goodman Games reprints (Keep on the Borderlands and Isle of Dread).
The later are easier not only because they are shorter but there is less complicated backstory and plot lines to keep track of. Even Dungeon of the Mad Mage is easier because prepping and running a mega dungeon is easier than trying to run a party through a novel.
I've been running Rappan Athuk from Frog God Games. This beast of a book is over 500 pages, with 56 dungeon levels, 22 wilderness areas, and over 100+ keyed maps and I am running AS A BREAK from the WotC books. With a mega dungeon like Rappan Athuk the party makes the story. The plots develop organically. Sure, you want to be familiar with the overall dungeon, but you are generally needing to read carefully over a small amount of content covering where the party is likely to be during your next game, and, if they end up somewhere you completely didn't expect, you can take a short break and quickly read over the area to make sure you understand any more complicated encounter or trap. Usually I don't need a break.
I thought maybe it was because I'm an experienced DM that I feel this way. After all, a LOT of people didn't like Dungeon of the Mad Mage. And it seems like many of the new DMs that 5e drew into the game needed their hands held and that the players expected a rich and intricate plot to take part in. But I watch my son who will be going on 13 years and he is turned off by the big hardcovers on my shelf and using graph paper and the online tool Notion, creates his own dungeons with simple plots that I enjoy just as much as the published material. And I like how most of my son's time is spend MAKING maps, MAKING monsters on D&D beyond, MAKING new making items on D&D beyond. I love how the main book he references is the DMs Guide because some of the tables are useful to helping you quickly MAKE things.
THAT is what is missing from most of the published material. Gaps. There is too much to cram and two few blanks to fill.
Now the benefit of being an experienced DM--and a busy, aging, and increasingly forgetful DM--is that when, despite all my prep, I get something wrong or forget something important, I just go with it and it becomes the adventure. The gaps in my memory become the gaps that are missing in the publication. Under-preparing can lead to a more creative and customized game.