In my opinion, the modules are poorly written these days and are rather easy to just blow through. The modules from back in the day were paperback and at most a total of 24 pages. In those pages they had all the important information you needed to either run the module as it was, or expand on it. It had history bites, maps you could quickly jot out properly, monster lists, the bare bones of how the adventure should go, ect.. Depending on how your DM wanted to run it, you could run it as a one-shot, a two day weekend event, or a whole month's long adventure. DM's had everything at their disposal with just a couple books and the module itself, no need for really anything else. Now, you have modules that are ONLY sold in hardcover or digital where you have to print it yourself, that have hundreds of pages full of nothing. No history, no backstory, no easily accessible maps to quickly draw out properly, nothing really. There's nothing in them for DMs to work with outside of small little text blocks that they have to read from and very short descriptions of what's in dungeon rooms. Overall, from a cursory glance the modules are poorly written from back in the day.
Though, there are reasons modules from back in the day were written better, and reasons why modules today are poorly written. Older editions of DnD, my own experience being mainly original, was that there were rules and monsters that were far more powerful than they are now, spells that were far more powerful and imposing than they are now, history was far more rich than it seems to be now. For example, if you were in a dungeon and you got to a room with a wraith, that wraith back in the day meant serious trouble, having one was an issue, having 2 or 3 of them were pretty much a death sentence without a cleric or paladin. Now, you can have a room of just one and it means nothing, have a room of 2 or 3 and it still means nothing, but it only just starts to get a little on the edge. Everything can be slept off and there are even certain effects that only hit once where they use to be a DOT. This is jus tone example of what I'm tying to convey, there are more of them, such as with diseases, poisons and such. Monsters today don't have anything to really fear, nothing to truly make them feel like fighting them would be a challenge. Sure, they have a CR rating but, that really doesn't mean much of anything.
Then there is the history bit. A perfect example of this is Tyranny of Dragons and chapter 4 where the characters are traveling from Baldur's Gate to Waterdeep. It says it takes 2 months to get from one to the other, but if you look at the map there is nothing between Baldur's Gate to Waterdeep aside from Dragonspear and Daggerford. Now, new players to the game will just run it and go, this is fun and I can just tweak things here, do this, add that, and they are fine with it. People that have access to the history of the Sword Coast and history from back in the day, they would know that road is FULL of little towns and outposts that help make that journey. It says that every 7th day is a day for resting of the animals, but if you know the history, you know that on roughly every 7th day, the caravan would hit a small rest-stop town that they can either get fresh horses or let their horses rest properly for the day. With that, a lot of the newer players go into Dragonspear and Daggerford and don't realize the significance of these places and just wander through and make stuff up, no realizing their history is massively rich and there is a ton more you could do with it. The module doesn't give you any of that, despite the hundreds of pages it has to go with, they would rather write about nothing of importance to the DM such as said history. A lot of people think chapter 4 is boring and either skip it completely or mod it so heavily that it's not even the same place. If the people at WoTC had even decided to dig into their own archives for it, they could have made that chapter better from the get-go instead of having people have to heavily mod it themselves. If newer, or even older, DMs wanted to mod the chapter still, then that's completely fine, but they should have made that far more interesting from the ground up. I mean, all this said, the history is out there, it just comes down to if the newer players are willing to put in the work or not to look for it, and unfortunately it seems not considering how many people I read that have skipped it.
These are just two examples of what I'm trying to convey. I still think modules for 5th are garbage and poorly written, but I also understand why they are. Monsters have changes greatly, rules have changed greatly, it's not the same game as it was back in the day; but, that still isn't a complete excuse for why the modules are poorly written, but it does explain some of it. WoTC had options to make them great and had a chance to offer newer DMs to have much needed information at had, instead of assuming every DM just knew all the history of the game they are playing. They added fluff and nonsense in the modules that wasn't needed and gave them a very bare minimum to get the game started, and that's barely. DM's really shouldn't have to go too far to get important information to make a module great, it should already be there, and then it's up to the DM to choose whether or not they want to use what's in the book or not.
In short, yes I do think DnD 5E is very much easier than other editions and does lead to some boring games, with WoTC to blame, but that doesn't mean DMs can't add mechanics or monster powers back into it from older editions to make it a little bit more exciting to play.