Let’s say that the big-picture mission is to create a world full of good times. That’s a world that’s full of minds, and those minds are reliably having a good time.
Right now, humans are pretty good at making more minds. We know how to do that. We’ve got almost 8 billion running at the moment.
But we’re not very good at reliably getting good times. A good chunk of those 8 billion minds live in conditions that are not conducive to good times: disease, oppression, hunger, etc. But strikingly, even for the small minority of people who have all the external conditions for success — people who are wealthy, attractive, physically healthy, intelligent — even for those people we can’t reliably achieve happiness.
This is the reliability problem. If the mission is to get to a world full of good times, we’re not yet ready to scale. We need to figure out how get minds to reliably have good times.