It sounds like the new teammates are too comfortable if their current learning rate is 2-4 years. That number could also be an overestimation, which reinforces the relative rank in the team.
This points to another "field of tension": when the value of the company is in the minds of the programmers (not in the code), how should an organization handle rank such that all team members become stakeholders in the most effective progress?
I suspect more like academic rank rather than "team lead" or "lead dev".
My field, medical device software, has very long product cycles. It's not that my teammates are taking a long time to learn, it just takes time for a project to reach maturity.
Additionally, we've all been learning to collaborate in a new mode, with immense distractions. Prior to our reorg, we'd never actually worked together before. And we all had our own deadlines we were trying to meet. The last 11 months have been pretty awful, ya know?
This points to another "field of tension": when the value of the company is in the minds of the programmers (not in the code), how should an organization handle rank such that all team members become stakeholders in the most effective progress?
I suspect more like academic rank rather than "team lead" or "lead dev".