But the ranking is not reflective of actual skills. That's the critique. Aside from very frequent open source contributors (and I think these people are the minority of devs), devs will tend to be "profiled" by this tool according to the dot scripts, university projects, Advent of Code, or other half-hearted projects they happen to have put on their Github. (Maybe I'm just projecting...)

The issue isn't that not everyone has a Github presence, the issue is that for most people their Github presence is somewhat unrepresentative of their actual job skills.

It is one dimension of many showing amounts of practice. I understand why that makes people sad, but that sadness just feels narcissistic.

I might be interested on people who can help me solve my particular problem. Those people might not be the same who have lots of commits on Github.

Then, logically, you would not hire them solely based on this one tool.