I disagree that Jr devs can’t be extremely productive in their first 6 months. The problem is mentorship. Many senior devs just suck at it and need training.

I worked a project for a large medical company recently in which I was the sole Sr. Engineer. I had a team of 3 junior engineers, one this was their second job, one that was fresh out of a code boot camp. I juggled all of the system design, architecture, IAC, as well as about half of the project planning with our pm all while also guiding and mentoring 3 junior devs.

The key is simply being available, setting up systems, tools and automation and above everything else documentation. I cannot stress this enough, if you had to learn it or figure it out, WRITE IT DOWN so the next person that comes behind you has it easier