Doctrine above features.
Mobile suits were invented to infiltrate colonies and harass capital ships. The latter task stems from Tomino's understanding of WWII combined arms, where the airplane became the dominant strategic element (as tactical elements they were effective in the form the dive bomber, but it is the level high altitude bomber which caused the biggest strategic damage). He transplanted carrier aircraft into toy robot story. The mobile suit is an all-terrain strategic element that affects violence better than the aircraft of WWII. Zeon recognized the strategic importance of mobile suits when considering them compared to mobile armor. Zeonic won the doctrine contest against MIP's mobile armor.
Mobile armor was MIP's theory that maximum speed and offense were the champion of the new warfare. The things you think makes a mobile suit so effective are actually dialed to 11 with mobile armors. The primary goal of the mobile armor is not infiltration and harassment, but simply total destruction. As it so happened, the Zaku was actually really damn good at killing capital ships, the incumbent primary element of warfare as late as 0078. So the bigger hurty-killy machine looks less than ideal when smaller hurty-killy machine is good enough with much higher mass production potential.
Compare the sizes of the three objects; mobile suit, mobile armor, and capital ship. You can see that the mobile armor is ostensibly the most compact iteration of the capital ship's biggest feature, firepower and travel. The MA is all gun and no command.
>>23350772Psycho Mk III has its own minovsky craft system. Its predecessors are shown to strategically search and destroy (ie Hong Kong, all of the AEUG) . Quin Mantha is a scaled up Qubeley; elite newtype MS tactics. Quin Mantha being as violent as Psycho shows why MA is a dead-end doctrine.