I know, building something up to win hearts & minds and so on in in fashion.
But in the case of Afghanistan, I simply don't understand why so many people focus on that and the fighting.

As I see it, we have a desired condition for leave
(central government is stable and powerful enough to gain control over the whole country)
and a minimal condition
(non-Islamistic forces are strong enough to suppress islamistic forces).

Why do so many people insist on building a western-style army for the central government, fighting the taleban and meanwhile doing good things for the population to avoid additional troubles?

Wouldn't it be simply possible to let the central government raise a well-paid, typical mercenary army and crush one warlord after another if necessary so that once the central government is powerful enough we could simply get out of that distant and geostrategically very irrelevant country?

I feel that the presence of infidel foreigners just helps the taleban recruiting effort. It's difficult to imagine for me that they could recruit in Pakestan as easily if they only waged war against Afghani muslim factions.