This only works if you hire enough really good engineers and have them spend most of their time mentoring, and most companies aren't willing to accept the senior engineers individual contributions on paper dropping to zero.
I disagree. Actively mentoring, like what this demands, is more supervisory. I do it with college interns all the time. It's not suddenly different because the pipeline doesn't originate with college. The process generally goes:
1. In weekly one on ones we may discuss a topic. I ask them to apply that topic.
2. They pick up sprint tasks and look to apply the knowledge they've gained.
3. They may ask some questions along the way; it's important that other engineers are also available for question asking - the same way peers may depend on each others knowledge.
4. You peer review the outcome in a PR.
Rinse and repeat.
I'll add I end up having to do this with everyone if they're fresh to industry or came from a place with poor standards for code writing and/or problem solving.
1. In weekly one on ones we may discuss a topic. I ask them to apply that topic.
2. They pick up sprint tasks and look to apply the knowledge they've gained.
3. They may ask some questions along the way; it's important that other engineers are also available for question asking - the same way peers may depend on each others knowledge.
4. You peer review the outcome in a PR.
Rinse and repeat.
I'll add I end up having to do this with everyone if they're fresh to industry or came from a place with poor standards for code writing and/or problem solving.