Generally, I think they're fine. Conceptually, I think they're fine. I used them all the time growing up with D&D (B/X and BECMI) and AD&D 1e and 2e. Even the 3rd edition stuff was OK.
My main problem with published adventures these days, is that many of them (particularly the ones from WotC that I have purchased) are not laid out with ease-of-use for the GM in mind.
I do not have time to read through the entire book and study it before I start running it. Now, maybe this issue has been solved in more recent adventure, but I remember a specific instance from one of the earlier adventure where the PCs encounter a specific NPC. In the NPCs statblock (in the back of the book), it lists what the NPC has. However, in ONE SENTENCE buried in a description in a later location which the PCs won't reach for several levels yet, it mentions that the NPC does NOT keep a particular item upon their person, but rather in a chest in that particular room (which again, the PCs won't reach for several levels and possible weeks or months of REAL time). Ergo, the NPC did NOT have the item when the PCs encountered them.
THAT WOULD HAVE BEEN USEFUL INFORMATION TO PUT IN THE INITIAL ENCOUNTER WITH THE NPC
That kind of stuff was rampant in the WotC adventures I purchased and attempted to run. They assume an encyclopedic knowledge of the entire book before you even started session 1, because they provided no adventure outline, no synopsis (other than what was printed on the back of the book), nothing to make it easier for a GM to run the darn thing. There were DM's Guild purchases available to mitigate some of that, but in my view, those shouldn't be necessary to keep me from pulling out my hair.
I found out that it was much easier and LESS work for me to run my own, original adventures, than to use prepublished adventures from WotC. (To a lesser extent, I found this also true of Pathfinder's Adventure Paths, though at least those are broken up into chapters, of a sort, that are kind of self-contained.) In my opinion, a pre-written adventure you purchase should save the GM time and effort, not make the game harder and more like work. I play the game to escape from reality for a bit, not do a College Cram Session LARP.
I've heard people say that Paizo's Adventure Paths, and WotC big adventure books aren't really written to be run, per se, but rather to be read, like some kind of weird game lit fic. I'm not sure I can disagree with that.