B4: The Lost City is a classic module for D&D. At one point it (in)famously stops giving full description of the rooms but instead lists monsters in each area and tells the DM to figure out why they're here themselves. Once the reprint will show up in new anthology, I'm sure people who complain online whenever WotC uses "ruling not rules" or "DM decides" or "these parts were left for the DM to fill in" in their design (and then continues buying WotC books to keep bitching and doesn't touch 3rd party or other games for some reason) is going to be normal about it. /s
Spelljammer and the OGL were what drove me to GURPS.
I don't need a book's permission to use my imagination. I buy a book to have play tested and balanced content.
Yea this is 100% the issue here. If I wanted to make content, I would, if I purchase a book with content for a specific setting or scenario, then there had better be that content in it.