It's always been a little vague, but I remember most of this forum a few years ago figured that midi-chlorians gave you a "limit," but how far you got within that limit was entirely up to training.
There were also the concepts of "force auras" and artifacts, rituals, sorcery, force walk, force drain, nexuses, and arguably Vaapad which amped people to a point where their count didn't matter. Legends authors tried to avoid natural limits by winding around midi-chlorians for 15 years.
Midi-chlorians manipulation even made it so you could theoretically change your count.
I'm not sure what Lucas intended with the whole "midi-chlorians" thing. He did have the "that's higher than master Yoda's!" line in The Phantom Menace, which could mean that midi-chlorians are the sole determiner of what makes someone powerful (besides training, of course).
Or maybe it was like the door explaination, where some people were more naturally talented than others.
I mean, he didn't introduce the concept to talk about power levels; I don't think he ever cared about who was more powerful in the force than who. I don't know if he even thinks of it like A>B>C logic, but rather Rock>Scissors>Paper>Rock logic. It's reasonable to believe that some people are more talented than others, though, so it's no big issue.