How Likely is a Real-World Attack Like the One in Netflix's "Zero Day"?

A new user in cybersecurity is questioning the likelihood of a malicious actor infiltrating our large-scale infrastructures and defenses, as depicted in the Netflix series "Zero Day." They mention the Stuxnet attack on an Iranian nuclear facility, which exploited Zero Day vulnerabilities to spread. The user also wonders what other methods could be used to infiltrate major infrastructures, shut them down, restart them, and leave no digital trace.