We never would have converted to Origin

I think we would have. Humans love organized religion. There are more than a billion Catholics and almost two billion Muslims on Earth. And in the rest of the galaxy, humans are already used to worshiping the Goa'uld, Asgard, or mythical ancestors.

Imagine how popular a religion like Catholicism or Islam would be if they also had viable hyperdrive technology. I think many of us would happily convert and the Ori would have to kill very few humans.

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they never would have let us get that far... then they'd have to share power

As far as we know, the Ori's concerns about sharing power only extend to other Ascended beings, and they don't have any problem with technologically-advanced human societies that worship Origin.