> If AI is capable of performing these attacks, what would stop AI from replacing the security engineers?

Because the threat model is one-sided - if an AI attack fails, the controller simply moves to the next target. If an AI defense fails, the victim is fucked.

Therefore, there is still value in being the human in Cyber Security (however you are supposed to capitalise that!)

There are still protections and mitigations that targets can do, but those things require humans. The things that attackers can do require no humans in the loop.