I don’t think GitHub cares about reliability if it does anything less than that.
I know people have other problems with Google, but they do actually have incredibly high uptime. This policy was frequently applied to entire orgs or divisions of the company if they had one outage too many.
(See also: Windows, Internet Explorer, ActiveX, etc. for how that turned out)
It's great that you're working on improving the product, but the (maybe cynical) view that I've heard more than anything is that when faced with the choice of improving the core product that everyone wants and needs or adding functionality to the core product that no one wants or needs and which is actively making the product worse (e.g. PR slop), management is too focused on the latter.
What GitHub needs is a leader who is willing and able to say no to the forces enshittifying the product with crap like Copilot, but GitHub has become a subsidiary of Copilot instead and that doesn't bode well.
It could be, some people are just terrible at their job. Lots of teams have low quality standards for their work.
Maybe that still comes down to leaders but for different reasons. You can ship useless features without downtime.