Then the non-pros never have the opportunity to learn from the pros and the pros never get a break which leads to employee morale and retention issues + tacit knowledge loss.
Pros get burnt out being constantly called on to crank out new features under pressure and never get to leverage their deep understanding in the maintenance phase.
Non-pros have no upward mobility (career progression) and get burnt out struggling to understand and maintain unfamiliar code without any guidance.
I've experienced a different situation where I was one of two pros – pillar may be more appropriate – in a team of around 15 devs – and wasn't recognized as such. I was working 70h/week on average (I never was paid for those overtime hours and my actual hourly wage was under the minimal wage), taking in charge every and any issue that may pop up, I was a reference when it came to knowing how our system worked and people would come ask me questions about the inner working of some part even when they had designed it ! I left disgruntled, and the other piller followed course because I wasn't here anymore to buffer the conflict he had with the CTO. In spite of the new hire and organizational restructuration to fill the gap, what should have taken 2 weeks to implement (a few hours to a few day in the redesign I had reimplemented at home in the weekend following my departure), took them 6 months. They had to distribute overtime hours to every dev, and in the end I received a call from the guy in charge of HR who told me the company was considering rehiring me at the condition I should behave ! Dude was fired eventually and replaced by a manager from the holding company.
As for pros needing training by other pros, I think it's more a question of culture. Once I was tasked with adapting a microservice to also run as a library, the challenge being we used JSON fields and now also had to store them in a mysql database that did not support them natively. I wrote an adapter that could have been released as a separate library because it was that generic, it took me 1 day of work, a 15 files long PR. But because it used a postwalk traversal on tiny json data triggered lazily upon accessing the specific field, cached in the ORM object for repeated access, it smelt funny to the CTO who proceeded to ditch my work away, spend the 3 following days adapting 350 files to try to get a highly specific solution then gave up, and decided in the end we'll have two separate versions of that system, in concurrent use, one as a lib and one as a microservice, hence multiplying by two the time it took to do changes to that highly repetitive codebase because "it was simpler that way".
You don't need to train pros, they have been training on their own since they are twelve.
Pros get burnt out being constantly called on to crank out new features under pressure and never get to leverage their deep understanding in the maintenance phase.
Non-pros have no upward mobility (career progression) and get burnt out struggling to understand and maintain unfamiliar code without any guidance.