The experience I want is to enjoy spending some time watching an interesting documentary and walk away with my mind enriched with some new facts and analysis. Instead, a lot of the time, it's interesting, but I walk away believing something that isn't true because whoever made the documentary was too lazy to fact-check, was unconsciously biased, or was even intentionally leaving out part of the story because they have an agenda.
Not all documentaries are this way, of course. Some are accurate and objective. The problem is I can't easily tell before watching. As a workaround, I can do a bunch of my own research after watching, but that's a bit of a pain, and maybe I'm better off just skipping the documentary and going straight to the research.
Unfortunately, for a documentary to succeed commercially as entertainment, it's not necessary for the audience to actually learn. They just have to feel like they learned something.