You've got a good point about the problem of using real-world concepts like 'cult' when talking about the Jedi. In our world, a cult generally has a pejorative feel to it. We see them as something dangerous and outside the mainstream, but the Jedi Order within the GFFA was a powerful institution, one which, while few every day citizens interacted with it, was widely respected and whose members were welcomed into the halls of power. Clearly, they didn't see themselves as a cult and would have probably been deeply insulted by the idea, and yet, they exhibit all the classic hallmarks of one.

I very much think the Jedi Order in the PT and Clone Wars cartoons was meant to be an object lesson about what happens when well-intentioned religious groups become more focused on retaining their power than living by their ideals. After all, the manner by which good people and institutions fall to corruption is literally the point of the trilogy.