Google bots can't tell if your content is good or not because they're robots, but certain things will signal that your content is good to rank high.
the length of your articles indicates if you can thoroughly answer people's questions so longer articles tend to rank higher.
how people respond to your content also sends signals to google if your content is any good. if people click to visit your site and read your page for 1-2 seconds and click the back button, it signals Google that your content is garbage and you lose rankings.
so how people behave on your site impacts your ranking as well. if people read your article, and scroll down, and even click links to other posts on your blog to read other posts then google takes that as good signals to rank you higher.
and if you get backlinks from other sites, you also rank higher.
but quality content is subjective. people have different ideas of what quality would be for a specific search string so google uses certain metrics to decide what to rank on the front page for certain keywords.