> If not, and you own the physical capacity yourself, wouldn't you do away with CloudFlare entirely?

Cost could be an issue. We had something similar (not in the same context) in a company I worked for before. We could shift traffic, but that would cost 2-3x more, so it was not the preferred path unless we had problems.

It surprises me that many (big) companies did not learn the lesson already. We had a similar thing happening already years ago with dyn in 2016 (https://en.wikipedia.org/wiki/2016_Dyn_cyberattack), and it was surprising how many companies relied on a single DNS provider.