Documentary occupies a strange space compared to every other genre on this list, because it's not really being judged on imagination or performance, it's being judged on how effectively real information and real people are presented. That fundamentally changes what "good" even means in this category.
Structure matters enormously in documentary filmmaking, arguably more than in narrative fiction, because there's no built-in plot to lean on. A documentary has to actively construct a compelling narrative out of real, often messy events, choosing what to include, what to leave out, and how to sequence information for maximum clarity and impact.
Access is another major factor unique to this genre. A documentary's quality is often directly tied to how much genuine access the filmmakers had to their subject, archival footage, willing interview subjects, unfiltered moments. Two documentaries covering the same event can differ enormously in quality purely based on what footage and cooperation the filmmakers were able to secure.
There's also a meaningful distinction between observational documentaries, which largely let events unfold with minimal narration or intervention, and heavily narrated or agenda-driven documentaries, which actively shape interpretation through editing and voiceover. Neither approach is inherently better, but knowing which style a documentary is attempting changes how it should be judged. An observational documentary criticized for "not taking a clear stance" may simply be doing exactly what it set out to do.
Bias is unavoidable in documentary filmmaking, every choice of what to film, what to cut, and how to frame a subject involves some perspective. The strongest documentaries tend to be transparent about their point of view rather than pretending to pure objectivity, since audiences tend to trust openly framed perspective more than a documentary claiming false neutrality.
On Rolio, your documentary ratings often correlate closely with your own subject interest as much as filmmaking craft, a topic you're deeply into may end up rated higher in your catalog regardless of technical execution. Because of that, looking back through your documentary ratings by subject area tends to be more revealing than browsing the category broadly.