I work at a FAANG-like company. The code base has almost no functional programming paradigms deployed. It’s a multi-billion dollar company from which I, an IC cog in the machine employee, became a multimillionaire through from the IPO. It’s wildly successful.

Is it all design-patterny OOP?

The vast majority of it is, unfortunately. That's starting to change, though, as we are hitting some pretty severe maintenance and performance issues, as well as being bottlenecks to making changes, that all the abstraction is obviously the root cause of. None of the services the team I used to lead utilized OOP (in the sense you're referring to), and the new team I lead will be making sweeping changes to move away from it under my guidance.

It served its purpose, but we've outgrown it.