We're talking about a country that's been used essentially as a pawn by the major imperial powers of each era for the last 200+ years. (This situation is not unique to Afghanistan - which is why many other countries have similar problems - but Afghanistan's geography compounds the effect).

The British, Russians, US, Ottomans, Mughals, Safavids - all of them have spent significant time and effort (not to mention military power) trying to secure the region for "their" side. All of them struggled with it, to the point where it's debatable whether any of them ever succeeded.

This situation continues on today - so no, I don't think Afghanistan can ever be politically stable as long as it continues to hold this role in global geopolitics[0]. Perhaps circumstances will change and we'll start to see a more stable regime emerge there, but it's kind of hard to force that when one of the major causes for instability in the last two centuries has been external influence in the first place.

EDIT: Unrelated to the answer, but I find the use of the word 'balkanized' particularly amusing given the etymology (it refers to the fragmentation of parts of the former Ottoman empire into many states that compete with each other for regional influence). Afghanistan is not part of the Balkan peninsula, but it did have its own fascinating power struggle with the Ottoman empire, and the breakup of the Ottoman empire in the early 20th century was a major turning point that influenced the current state of Afghanistan today.

[0] I'm not sure any country really could be, for what it's worth, but we're talking about Afghanistan.