It's more likely that there are a lot of false negatives in CircleCI's hiring funnel. The issue isn't "there aren't enough good developers." There are plenty of good developers. It's possible that this sample of 1000 developers came from really bad sources (there's not enough information provided to determine the quality of their sourcing). For example, referrals convert at a rate of 57% to the screen (compared to 13% when sourcing). Recruiting agencies convert at 59% (although you'll be giving away 10-30% of first year salary for that). It could be that this sample is purely inbound applicants, which convert the lowest at 13%. [1]
We have benchmarks to understand how well a company is converting at each step in their funnel. CircleCI is converting well in 2 of their funnels, but the other 2 are underperforming significantly per my other comment in this thread.