I understand that there are things in software development that cannot be learned in school, even in a CS degree. As discussed, for example here, these include things like best practices, design patterns, testing etc.
But what if one was not just learning things theoretically, but on the job? I am referring to being a solo developer, perhaps at a startup with no previously established software group. An advantage of this might be the opportunity on building the entire software stack from scratch, which seems to be a rare and invaluable experience that someone working in an established team might never get to encounter!
On the other hand, the solo developer might miss out on things like daily mentorship, constant peer-wise code review etc.
What if there are mitigating factors: Say if the solo developer had access to experienced developers for occasional consultation, but not as colleagues. Or if the solo developer has the theoretical underpinnings, say from a formal education in CS and knew what and where to look for information?
The key question: Are there things in software development that simply cannot be learned unless working in a group? If so, is this 'gap' a deal-breaker for future employment as a developer outside of solo development?