Recently a friend of mine, who is reasonably well rated on Codeforces (1800+) talked about how Codeforces/Atcoder/Codechef tasks are very important in teaching us how to implement efficient code and how it is very important when you are writing general libraries (think Tensorflow, PyTorch, React, Express etc). I don't agree with him. I told him that people like Linus Torvalds wrote a lot of code that a lot of critical infrastructure uses. These people wrote fast and fault-tolerant code without having any experience in algorithmic competitions. But his argument is that the low-hanging fruits of algorithmic optimizations have already been achieved and in the coming years only those who have good experience with competitive programming will be able to improve these systems reasonably. What do you guys think?

Is it really that to learn to write fast and fault-tolerant programs you need competitive programming; or is there a better way to learn the same? If so, what's that better way?

Also, what, in your opinion, is a real-world skill that competitive programming teaches?

[P.S: I can already sense the downvotes coming after me.]