There are infinite ways to organize teams so your concerns are addressed. For example, you can have primary, secondary, and backup developers for each component

There are infinite ways to organize teams so your concerns are addressed. For example, you can have primary, secondary, and backup developers for each component of the system. That keeps you bus factor down and makes it more clear what the progression of responsibility looks like. But, absolutely, a lack of peer review, authentic feedback, and general teamwork causes all sorts of issues in so many ways.