But isn't a CDN a commodity? I.e., you can switch to a different one with almost no effort.

How does that quip go again…there are only two difficulties in computer science, cache invalidation, naming things, and counting.

Going from one CDN to another can be infuriating even at a surprisingly small scale. Mostly (imo) from caching semantics and counting.

It's not really a commodity when Cloudflare is often cheaper, simpler and provides a better service compared to it's competitors.

For it to be a commodity there would be no good reason to pick Cloudflare over any alternative and this absolutely isn't the case.