I had a former coworker who moved from the medical device industry to similar-to-cloudflare-web software. While he had some appreciation for the validation and intense QA they did (they didn't use formal methods, just heavy QA and deep specs), it became very clear to him very clearly that those approaches don't work with speed-of-release as a concern (his development cycles were annual, not weekly or daily). And they absolutely don't work in contexts where user-abuse or reactivity are necessary. The contexts are just totally different.
It is perfectly possible to engineer for faster cycles without losing control over what your code can and can not do. It is harder, for sure. But I do not think it is a matter of this absolutely not working, that's black-and-white and it never is black and white, it is always some shade of gray.
For instance: validating a configuration before loading it is fairly standard practice, as are smoke tests and gradual roll-outs. Configuration fuck-ups are fairly common so you engineer with that in mind.
