At least when I was at Uber (left in mid-2019), this was absolutely the case: most services weren't CPU-bound, but a few were. Rewriting the CPU-bound services in C++, Rust, or some other language might have helped, but would have required a _ton_ of well-understood, reliable libraries for networking, observability, authn/authz, database access, etc.

In nearly all cases, there was plenty of room to make the Go service faster. A more careful choice of data structure and algorithm, finer-grained locking, fan-out across a goroutine pool, or just avoiding a zillion heap allocations solved most problems. I don't recall any cases where Go was simply incapable of meeting our performance needs.

As a side benefit, services with more stringent performance requirements often exposed inefficiencies in widely-used libraries. Optimizing those libraries made every Go service faster and cut our overall compute spend. Avoiding rewrites in C++ or Rust let those wins add up over time.