Well, I agree that manual gearboxes are more powerful, reliable and easy to maintain. When automatic gearboxes first appear, we also refused them for the sake of reliability. But now, it's at least 20 years after the automatic gearbox first introduced.
But what happen when you got stuck in a traffic jam? Automatic gearboxes ease your driving at slow speed, and give you all the convenience you want. The same in tanks. Let's assume that all tank drivers are well trained and highly skilled. When you drive a manual-geared tank, both of your legs and one of your hands are occupied, because you have to change the gear position all the time
. But in automatic geared, only one leg is needed to reduce or add speed. It's just like you are playing a toy. So, if two skilled tank drivers, one drive automatic and the other drive manual, fighting each other, who wins?