Using a WWII era formation in the jet age. This alone reduced their air combat power to 1/4th of the Navy's, and exacerbating the manpower problem. In general a tremendous amount of institutional butthurt from being forced to use Navy planes and missiles appears to have prevented them from updating their tactics and otherwise following the Navy.

Dependence on their own ineffective missiles such as the AIM-4 Falcon (only in theory useful for knocking out big bombers) and their own versions of the Navy's Sidewinder.

Totally inadequate training, especially for replacement pilots as they rotated the first set out. The Navy was "lucky" that the single most difficult thing you can do in an airplane is generally considered to be landing on a carrier so they couldn't drop standards, but they also e.g. set up the Top Gun school.

Inability to learn, to for example realize the above meant their pilots were firing their missiles out of envelope too much. Or that their rough handing of missiles prior to putting them on planes resulted in many more of them failing. Not (hardly as much) a problem with the Navy.

Unlike the Navy, they were unable to provide good real time guidance to their pilots (when close to the shore, their pilots could benefit from the Navy's assets). They also found it difficult to impossible to put together a working system to get real time warnings to pilots from intercepted North Vietnamese transmissions.

Those are just the big ones off the top of my head, air combat focused, there's lots more.

As for the 150,000 man Army, what they most critically did with smart bombs plus massively better constraints (or lack thereof) from the White House (LBJ -> Nixon) was to destroy the logistics supporting it. Yeah, air strikes further south were very nasty, but without fuel etc. a mechanized army withers on the vine and is less able to deal with close in threats ... e.g. easier to hit an armored vehicle if it's run out of fuel....