Jordan Walke and Miso Hevery are outliers working at companies that pay a lot. An average company is not going to be attracting talented engineers with strong fundamentals. They are going to be attracting engineers with average aptitude and average fundamentals.
An average company, paying average wages, solving average problems is better off getting an average developer specialized in the area they need.
This is only true because average teams get annoyed at having people trying to push the project along in ways they do not understand. In most of my jobs, average people really appreciate stability and do not like change. To fit in, you end up having to do less work and transfer your energy to side projects or hobbies
An average company, paying average wages, solving average problems is better off getting an average developer specialized in the area they need.