Hi Gunns. I gotta say I'm (pleasantly) surprised you took the time to explain all this, it's greatly appreciated.
Because modders aren't paid, the credit in YouTube videos and other such places are pretty much the only recognition they get. But the kind of maps the modders appreciate aren't the same maps your viewers appreciate. Modders love to see the engine pushed to its limits, innovation and originality, creative flair. YouTube viewers are mostly drawn to videos because of the personalities behind them, i.e. yourself and Meaty, and occasionally the gimmick (e.g. "Game of Thrones Zombies" is guaranteed to get hundreds of thousands more views than an original name no-one's heard, or a generic name like "night of the dead"). So, even if the modders are credited, there is naturally going to be hostility from modders who spend months, sometimes years, on their passion project, only to see a low-effort four-walled box get the same response, if not fifty times as many views.
Personally, I think what you guys are doing is absolutely fine, even more so after your post clarifying things. I'm glad you've reached out to the community, that proves you care, which puts you miles ahead of many other youtubers. I don't think modders should be so pissed, I just understand why they are.
Thank you for taking the time to post this, I certainly appreciate it, I'm certain the community does too.