If outages make headlines and stop whole companies in their tracks worldwide, that’s critical infrastructure, not just network effects.
As the centralized git repo, it allows devs to collaborate, by exchanging code/features, tracking issues and doing code reviews. It also provides dependencies management ("Package") and code building/shipping (GH Actions).
Sure, if you usually spend one day or more writing code locally, you're fine. But if you work on multiple features a day, an outage, even of 30 minutes, can have a big impact on a company because of the multiplier effect on all the people affected.
This is a sign that their CTOs should be replaced. Not that github is critical.
They should fucking learn how to code because no one in their right mind would depend on such an external service that can be easily replaced by cloning repos locally or using proxies like Artifactory. Even worse when you know that Microsoft is behind it.
Yes, most companies don't have good practices and suck at maintaining a basic infrastructure, but it doesn't mean GitHub is the center of the internet. It's only a stupid git server with PRs.
I feel like you’re missing a few features here