I work for one of those tech giants that I think falls into your "pro" category in a role that you could call dev ops. I used to work in a much smaller startup. The comparison of a tech giant's stack to large, growth stage startup tech stacks is like comparing trains to trucks. It's a qualitatively different problem because the difference between a few thousand and a few hundred thousand servers is Murphy's law.
In other words, I think there are two answers to your question of "what do the pros use?" The first answer is "Kubernetes, because that's the right tool for the job." The second answer is "My product division has an internal team the size of a growth stage startup, and it's specifically dedicated to solving server scaling problems, and that's just my product division."
Another analogy would be the question "how would an F1 team solve this problem?" One answer is "you don't need an F1 team for that", and the other is "first, hire an F1 team, then have them build all of the custom tooling the F1 car needs."