I suspect, however, that the gap between designs that are realizable for amateurs with limited training, and the ones that are realizable for professional teams

I suspect, however, that the gap between designs that are realizable for amateurs with limited training, and the ones that are realizable for professional teams is wider than in software. So somebody like me, who did two standard cell based ASICs 25 years ago, probably would have to add a sizable safety margin to produce a reliable chip, and would achieve nowhere near the performance of a pro team at the time.