If shipping something requires a 'team' – coordination between specialists (or worse, multiple 'owners') – it'll be harder than when each cross-cutting feature

If shipping something requires a 'team' – coordination between specialists (or worse, multiple 'owners') – it'll be harder than when each cross-cutting feature can be done by a broadly-capable/empowered 'full stack' person. (At least, that's how I interpret the OP, and don't understand your perception of any tension between 'full stackers best' & 'teams unproductive'.)