What made the QF 32 Pounder unsuitable for Tank use towards the end of WW2.?

I know what you are going to say it's too big, but looking at 3.7 Inch AA batteries (As you know it was based on) the rear breach area of the gun (Sorry I don't know what the rear gun section is called) doesn't look that much larger than the 8.8cm L/56, L/71 guns and American 90mm guns. I am interested to know if it was the gun, the guns transport platform or both that made the 32 Pounder to bulky and time demanding for tank or tank destroyer use. I'm not sure if the 32 Pounder has 2 part ammunition like the 3.7 Inch it's based on. I love love the American (I think the chis of an M24 Chaffee tank) SPG mounting the 150mm? Long Tom. The Long Tom I imagine would have been just as bulky, probably worse than the 32 Pounder gun to field when utilizing it's platform (like on the doentary Patton 360 against German Panzer's). I wounder if the 32 Pounder might have been mounted in a similar war or in a superstructure like a big Archer (But not back to front.). Cheers John.