Formula 1 has got itself to the point where it's no longer about the 'hero' driver, it's about how much money you have to develop the chassis and power unit. It's a sad state of affairs, but that's the way it is.
The competition between two team-mates will always exist and, yes, one driver will normally stand out against the other. In reality, that is the only measure of their individual talent but when the car is not up to it, neither will be able to find that bit extra.
Mercedes, Ferrari and Red Bull showed in in 2017 that when the car was good, both drivers were in competition. But more importantly, Lewis Hamilton, Sebastian Vettel and Max Verstappen showed they had that bit extra against their team-mates.