Many of the people working on those fan films are skilled, and I mean
professionally skilled. They're often the same crews working on TV commercials, music videos, documentaries, TV shows, etc. It's just that they're in career holding patterns while they build up contacts and resumes in order to move up a rung. In the meantime, they're working for charity rates or "mates rates" or even completely
for.free for buddies they got to know back in film school. Just look at that Darth Maul making-of; the equipment they're using is fully professional, the techniques they're using are professional. They look like they know what they're doing. But as you say, often it's the talent (i.e. performers) that let them down (And the scripting and conceptual prep work can be lack lustre as well.)
TC