But in Obi-Wan’s time, or even Qui-Gon Jinn’s, how was there any real challenge for a Jedi, outside of fellow Force users, like Sith Lords? Their were numerous Jedi back then and they were all well trained and adept witht he Force, and not late bloomers like Luke.
It just seems like with all their abilities, any fights they had would be pretty boring. I mean, apparently the Sith had been extinct for a long time until Darth Maul showed up.
For over a thousand generations, the Jedi Knights were the guardians of peace and justice in the Old Republic. Before the dark times, before the Empire. - Obi-Wan Kenobi, A New Hope.
You pretty much answered your own question didn’t you? Not much happened before the Sith showed up because they were so powerful, like you said. Not to mention the Jedi weren’t overthrown by sheer force, it was Palpatine’s slow manipulation. By the time Order 66 came around:
Our ability to use the force has diminished - Mace Windu, Revenge of the Sith.