Just to pile on, I have had people who complained that they should have been a senior dev because they knew the most about algorithms and the internals of compi

Just to pile on, I have had people who complained that they should have been a senior dev because they knew the most about algorithms and the internals of compilers, languages, libraries, and CPU's. Those same people couldn't communicate that knowledge to others and couldn't design complex systems containing multiple independent components, but they felt since they had strong technical skills that was all they needed.