suspicions or complaints that I kept hearing was that there was just too much (compromising) information in it. That intelligence gathering was difficult and most of it succeeds on small wins and tips that can lead to other small things, that eventually can give something conclusive or actionable, and that this dossier had so much info that it was like a piece of spy fiction.

My thought at the time is that might usually be the case because spies are typically dealing with other sophisticated actors who really know what they're doing. I thought the whole thing was true or at least extremely plausible right away because the people they investigated are clueless, arrogant idiots.