I always wished mediclorians had just been a byproduct thing, something that went WITH being force sensitive, not caused it. "what did you do?" "I took your medichlorian count" "what's that" "they're these little organisms, the live in all of us, but they flourish in those with a strong connection to the force. You should see master yoda's count, the little devils love him."
The EU had "force detectors" that were used to find possible students during the old republic era, and the empire used them to hunt down jedi, or find new "students" for whatever the emperor wanted.
They also had force sensitive lineages in the EU too, but it was never a sure bet. being from one of those families just hedged your bets.
I was over all pretty please with how IX handled the shake up to its plot. They did about as good a job as they could with having to fit a whole 8th movie in the first 20 minutes of the film. Unfortunately, I think that sort of loss of time available for telling a new story, meant they had to go with "ehhh, I guess palpatine spent the last few decades building mini death star things. they'll have to blow those up"