An Army analysis after WWII found that only 14% of tank rounds fired were fired at another tank. Most of the rest were against stationary targets and personnel. While vehicles are great, they are not as flexible as a two man portable anti tank rocket team.
Many years ago while visiting the Army Museum at West Point, I was enthralled by a beautiful diorama showing a German infantry man crouched behind a stone wall and getting the better of a Sherman tank with a Panzerfaust. As I stood there looking at this, a small boy came up and said “Look at this grampa; how cool!” Then I heard behind me a voice with deep German accent say in a somewhat disgusted tone, “Ya, but you had to be really close, and you would be killed”.
Tank versus tank, like fighter versus fighter, was never the raison d’etre for either weapon; it developed naturally in the course of actual warfare.
Tanks were originally intended to attack stationary targets and personnel (as you wrote), and fighters were originally intended to attack bombers (which is why the USAAC/USAAF called them Pursuits, not Fighters). In fact, tanks were largely viewed as mobile artillery pieces.
Because American tanks followed outdated WWI/Interwar field artillery standards for Guns - short-barreled and low velocity guns to preserve barrel lining for very long life (much longer than the real-world life expectancy for the tank itself) - the 75 and 76.2 Tank guns were soon inadequate. As a result, the M10 and M36 Tank Destroyers became highly valued when tank warfare was necessary.
As I recall, even when they used the 76.2 - versus the 90 - they had a longer barrel for better ballistics. (That is old memory; I could be wrong.)
George Patton was a brilliant tactician, but he was mistaken in maintaining the adequacy of the M4 Sherman: It had a high profile (radial aircraft engine), narrow tread (obsolescent non-Christie), and a low-velocity gun (whether 75 or 76.2).
That is why the British did for the Sherman what they did for the Mustang: upgraded it. They gave the P-51 the Rolls Royce Merlin; they gave the M-4 the 17-Pounder (76.2).
It was called the Firefly, and it was offensively equal to the challenge of taking out Mark IV, Panther, and Tiger tanks in frontal assaults. The British used to hide a Firefly in a squadron of normal Shermans; the others baited the German tanks to engage, and the Firefly took them out.