He also argues that Israel struggled in its 2006 war with the Iranian-backed militia Hezbollah -- which operates more like a traditional army than a terrorist group -- because the Jewish state had spent years focusing on counterinsurgency. His conclusion is echoed by a historian at the Army's Combat Studies Institute, who concluded in a recent paper that Israel lost the war because "counterinsurgency operations had seriously diminished its conventional war-fighting capabilities."
The observation that Hezbollah operates more like a traditional army is not an accurate one, but it cuts the heart of the argument.

I concur that there is ample evidence that over focus on COIN erodes formation fighting skills, but only if you allow it. This is not a given. (The British Army between 1976-93) It is a product of poor doctrine and understanding. Even the idea that there is COIN and then there is something else -called War-fighting- dodges the hard question, and leads to a false dichotomy.

NOTE: The IDF started as insurgents and switched effortlessly to formation war-fighting skills in 1948, and won! Then fought COIN continuously, apart from breaks for formations level operations in 1956, 67 and 73. - though I admit that it's COIN Ops of the time were typically British and thus quite brutal in nature, by today's standards, - though less so than French methods.