I think you missed the "critical path" part. Why would your product stop functioning if your admins can't log in with IAM / VPN in, do you really need hands-on maintenance constantly? Why would your product stop functioning if Office is down, are you managing your ops in Excel or something?
"Some kind of dependency" is fine and unavoidable, but well-architected systems don't have hard downtime just because someone somewhere you have no control over fucked up.
Since 2020 for some reason lot of companies have fully remote workforce. If the VPN or auth goes down and workers can't login, that's a problem. Think banks, call center work, customer service.
"Some kind of dependency" is fine and unavoidable, but well-architected systems don't have hard downtime just because someone somewhere you have no control over fucked up.