XC is both a team and an individual sport. That is why there are awards for both the team and the individual.
The coaching philosophy must show appreciation for both of those aspects because that is what defines the sport.
Disregarding either one, changes the sport.
Fortunately, there are ways to concomitantly address both of those facets of the sport of XC. The coach has to coach. If the guy is inept, then his only alternative is to guilt the faster kids into slowing down.
In your example, what if 3 & 4 get the altruism bug and decide to slow down to help 5? If they do not, wouldn't that be perceived as seeking personal glory? Hopefully there are no Jack Black lookalikes in the bunch.