Purpose of the MBT?

[Fuchs]

Sure, tanks of WW2 were technically very different, but when used correctly, they did things known to work in WW1. The Conceptual use stayed very coherent.

...except that they as similar to each other as were medieval knights to Celtic nobles.

The WW2 tanks were - with exception of assault guns, tank destroyers and infantry tanks - an operational enabler while it was merely a moving pillbox for tactical support in WW1. All WW1 tanks - even the Whippet - were either infantry tanks or carrier vehicles.

I fail to see that 'conceptual use' in a Tiger2, Chaffee, Pzkpfw III or T-34.