I think using mystical microbes to explain how spirituality can be channeled into superpowers raises more questions than it answers.
Surely the technology would have existed or could have been developed to isolate/propagate/synthesize/transplant midichloroforms or whatever into beings that otherwise didn't have them. It's been a while since I watched eps 1-3 but didn't they implant them into a droid?
If they could make an army of cloned fettes, they could have just as easily made an army of cloned (perhaps even improved) yodas, or anakins, etc.
Without jedi-chlorophyll, the relative scarcity of jedi and sith could be explained as a function of some combination of prejudice and disinterest. Anyone with the interest, devotion and proper training can strive towards becoming a yogi or 7th degree exalted master of ninjitsu. Some will actually attain that goal. Most people don't want to make the sacrifice, put in the work, or dedicate their life to the cause. Most people just want to be left alone and live their lives.
Lucas could have gone a different route and made some poignant social commentaries. Instead it feels to me like he rested on his laurels for 10 years and then copped out with a flismy mcguffin unworthy of the universe he created.