And this kind of back and forth between you two is why truisms are silly.
What are we even talking about? Aren't we supposed to be talking about how much lore is too much vs too little, not just blanket statements like more isn't always better? Let's look at the actual books and the actual points being made!
There are about a dozen domains in Ravenloft that I have no idea how to use. I could not read them and prep a game for them quickly or efficiently. I could prep the game. But I could not do so quickly or efficiently, because there is so much stuff I need to make. For example, a good domain is the one with the werepanther Dark Lord. That domain has a good map (good!), enemies, a goal, what the NPCs act like, and is a strong scenario I can drop into any game. But, on the other hand, there is "The Carnival." I do not understand The Carnival. It is very hard for me to grasp what my players a really doing here, and what this domain is really about. And that's because the domain just needs about 2 more pages worth of content and/or explanation for it to really click with me so I can efficiently and easily prep the game.
"But Shardstone," I know you are thinking, "That doesn't mean others have that issue!"
I'm sure there are people who have played the Carnival just fine. They probably already had a lot of ideas for it, and were loaded up upon seeing it, just like I was for (checks name) Valachan. But, objectively, adding these 1-2 new pages to the Carnival cannot take away from it. It could only add to it. And if you add those 2 pages to Valachan as well, even better! It does nothing but increase the quality of the book!
The fact that it seems we are losing more content does not give me good heart. In Radiant Citadel, this issue seems to be middling. For example, the "Trail of Destruction" region is AMAZING and super solid, I love it! But, if we do the first adventure in the book, still written well mind you, I don't really know what to do with the setting outside of the limited Night Market adventure. There just isn't enough page count to point me in the right way. Did we really need to keep RC down to 198 pages, or could we have gone 252 and just added some more gameable info, like some more setting-unique monsters or challenges, to really enhance the adventure? Would the book be worse off for this content? I sure don't think so!