Technically all outages are "human mistakes". Humans build hardware, write software, configure and maintain systems, and manage other humans. Which is why explaining an outage as "human error" is not constructive.

There are known methods to create systems that are resistant to human error: automation, checklists, testing, etc. Humans will make mistakes-that is a certainty. A solution to an outage will be to employ these techniques, not tell your team members to not make mistakes.