Uber's only able to set that cutoff because everyone rates 5 no matter what.

If people provided informative ratings, the cutoff would be adjusted. Uber's policies can't make the rating system worthless; the raters are doing it.

This isn't true. Uber has always had a minimum cut-off for driver ratings, and it has always been around 4.6-4.7. Uber set that expectation, not the riders.

So, according to you, if riders started rating drivers on a 2-centered scale, Uber would fire every driver before noticing the shift?

I stand by exactly what I said before: Uber is only able to set the cutoff it does because of rider behavior, and if the rider behavior were different, Uber would adjust to it, not the other way around. The riders have all of the power to determine what ratings mean, and Uber has none of that power, because the riders are the ones who set the ratings. No one at Uber is enough of an idiot to deactivate every driver on the platform because none of them reached a number that Uber made up. Or even to deactivate 70% of drivers because only 30% got perfect ratings.

That's because the riders have always dumbed down the 5-star system into a binary "one-star-or-no-star" system since the inception of Uber. Uber thus had no choice than to set the cutoff at this number.

Uber had the choice to drop the 5-star system and replace it with a thumbs up/thumbs-down system, or a minus/check/plus system, or a “click this if your ride sucked” system.

Uber had lots of other choices, too.

True, and I would like any of those better than the idiocy that is the 5-star system. But the "no choice" statement was directed at where they set the cutoff in their existing system. With their lie of a rating system, they have to set the cutoff at that point, or they would either not even ban the worst offenders or end up with no drivers at all.

They don't have to use a simple average.

That would be much better. At least it would be obvious to everyone what the rating means.