As someone who watched previous coworkers, who are older, go through the interview ringer, I can sympathize with the author on the pigeonhole one can get stuck in due to seemingly trivial reasons: I don't have a classic CS background, people think I'm past my prime, etc.
These aren't imaginary problems, and I struggle to believe that I would be all "go-getter" and "pull yourself up by your bootstraps" after continually being rejected, too.