In theory, a process could just return an error for that specific operation, which would propagate to a "500 internal error" for this one request but not impact other operations. Could even take the hint to free some caches.

But in practice, I agree with you. This is just not worth it. So much work to handle it properly everywhere and it is really difficult to test every malloc failures.

So that's where an OOM killer might have a better strategy than just letting the last program that happen to allocate memory last to fail.