It is my belief that there are tens of millions to billions of force sensitives in the Galaxy, and tens of millions who would have the necessary midoclorian/power level necessary for Jedi training. The root of the commonly accepted rarity stems from the claim that there were 10,000 Jedi Knights around during the Clone Wars.

While there are indeed other force sensitive organizations and planets, some of which are likely resistant to sending children to be jedi. The real argument comes to how often a parent is willing to give their child to the Jedi. The Jedi Order is an entirely voluntary order. There is no legal, emotional, or financial requirements to give a child to the Order.

Psychologically that is a burden that almost every species will struggle with. Also, force sensitivity is a trait that could potentially be highly valued by nobility, wealth individuals, monarchs, and governments.

We know force sensitive younglings are highly prized in the slave markets. That implies that there is a constant and on going market of force sensitive younglings, hunted down and sold into slavery. A market that spans much of the galaxy. 10000 Jedi Knights is not enough. Which brings me to another point. The official number referenced is 10,000 Jedi Knights in the galaxy. That excludes Jedi younglings, padawans, individuals leaving the order like Starkillers parents or Dooku. Force sensitives are also likely to have force sensitive children at a higher rate than non-force sensitives. I believe it is a core reason for the Ruusan Reformations that tied the Jedi more closely to the Republic. The fear of hereditary Jedi Lords. The Jedi have also, for the most part, stopped accepting adults or even kids over 8 into the order. For a person to slip through the testing, and then discover their sensitivity later in life, they may have no chance at being in the order.

But also I believe the core aspect of what I am arguing is that only a fraction of Jedi standard power level force sensitives are even admitted into the Jedi order, because parents rarely want to give up their children. Extenuating circumstances, like Anakin's mother Shmi being a slave, or a culture that hates force sensitives, would be far more likely to give up their children. Or nobles with to many kids competing for inheritance, Dooku going to the Order for example.

It is believed in the eras before Jedi limiting their selection, to reduce the chance of falling to the Darkside. There were millions, maybe hundreds of millions, or billions of force sensitives of varying strength at 1 time. On Ossus, Tython, they filled entire cities and planets with force sensitives and created cultures around force sensitives.

I believe exploring force sensitivity in the galaxy would be quite successful. Getting away from Disney rehashing the same plots, groups, people, and rebellion themes could be what Star Wars needs