See, there is slight difference in FAITH/BELIEF and REAL WORLD.
1) It is good to repeat belief that Royal is defensively more solid, but when one would watch every minute that both of them have played this season, then you'd get much more defensive blunders from Royal. And sure, he played more too. But I think the lowlight reel would be more awful even considering playing time.
2) Not talking about best performances, but let's look at the worst - Royal game against Woolwich away... he was fooled and stepped past countless of times. He let the team massively down way before he was sent off. There is no such catastrophy to be presented by Doc.
3) It is nice to repeat and repeat the age, but for fuck sake 24 yo is not a kid anymore. If decision making, crossing, timing and everything else is just not there... then it is not there. These are something that are drilled into at an early stage of training. Sure, you can give chance to like of Traore and expect him to "add end product to his game" for all you like. But it is extremely unlikely.
4) I MYSELF have UNDERSTANDING what Conte might require. But I have 0 tools to bring them to life. Same goes for Royal unfortunately. And this has been proven in more instances then Dohertys inability, yet Doc had more to show for.
5) If you have two fairly poor options, for one you could generate money from and from other you could not. Then rational option would be actually cash in from the below-standard player who can generate some return and use the one that cannot. I mean - if you have two cars but need only one. They are of equal comfort, reliability, fuel economy, etc. But one you could sell for 10 000£ and other you would have to give away free... then obviously you would sell the 10k worth car and keep using the one that would not have value?!?