And you will never form a team at all at international level if you don't keep continuity of selection and allow units and players to build around their understanding. The moment you introduce players who haven't really been part of the team you lose that. That is the reality of international rugby these days and why it is harder to lose a shirt than it is to gain a shirt. And that is the same in every country.
Now, you asked about Tuilagi, so I answered about Tuilagi. It is not a clarion call to keep picking the same XV every game until they get injured or retire - although basically every international coach wants to do that - it is a reflection on the varying contributions of Tuilagi and Joseph to the England rugby team to date. Joseph held his end up without looking much of anything in South Africa and done well against undemanding opposition in Argentina. Not bad, but he's proven very little. Tuilagi has been staggeringly successful for us and, while there are lamentable gaps in his skill set, he has proven the ability to rip holes in any and every international defence. So yes, selection in important games does go "Manu - you're fit - you're not imploding - shirt's over there" and that will not change until Joseph finds an opportunity and takes it to show he can perform to the same level.
Not every international player has that luxury. Ideally no player has that luxury, but sometimes that is the situation. If you've got a player who's not been consistent, not given a lot, they're under pressure. If they have rivals of equal stature, they're under pressure. Ashton should be finished by now. Guys like Care, Lawes, Morgan, they'll always be having to perform strong. But that is not the situation here. To repeat myself, Manu has not been the first, and Jonathan Joseph is not the second - and neither is Henry Slade. Burrell is the closest thing going to that rival. There is no way that Joseph's couple of strong performances and short hot streak of form makes him Manu's equal.
Tbh, I'm not sure he's even Burrell's equal in Lancaster's eyes.
Disagree if you like, but get used to disappointment, because that is the way of international rugby and that's an assessment of their international records who likes Joseph a lot as a player. I mean, if Lancaster is going to drag Twelvetrees back from injury to replace Eastmond after he carves the All Blacks apart, does anyone really think Joseph's gonna keep out Tuilagi?