Earlier quoted context omitted.
Yes, that young, entrepreneurial programmer can be found, but won’t have the domain knowledge. Look at the examples above. You can’t sell Marine mapping software without knowing something about marine navigation. You can’t sell beekeeping software without understanding beekeeping. Plus you need the general business operation skills. Finding a programmer who knows beekeeping and wants to take on a low growth business…
Yep. There may be 'takers', but will the existing customers want to work with them? So many solo/indie niche packages are built on the relationships, and replacing those - and the trust around them - is hard. A client told me about someone they knew who did ballroom dancing software - it kept track of competitions, standings, etc. And... it seemed like decent money, looking at the pricing, and the size of the market.…
Regarding your "The One Way", sometimes that one way is actually the one that works better, as it was developed and fine tuned over the years by a dedicated programmer that had constant feedback by users.
Probably that ballroom dancing software had a way to input (or present/output) data in a form that makes sense to the users.
When suddenly comes the new (otherwise brilliant) programmer that - knowing nothing on the specific field - invents his/her own way to input data or render it that the users find awkward or slower or less intuitive or whatever, with the new program that cannot import old data (or imports partially), that cannot use the same B&W printer because the output is highlighted with colours and not with bolding/underlining, etc..
No surprise that the users of the old software (if it is still working) won't jump on the new bandwagon.