Just logistically speaking, imagine needing to send dozens of different types of dozens of spare parts to different sections of a thousand-mile wide front line, with different types, shapes and calibers of ammunition as well. These tanks will likely just be abandoned after they get even slightly damaged.
The US only looks incompetent for ‘losing’ $trillions of its military budget while other militaries can account for their spending. When this is all over, the US will be able to say, ‘look: every country loses a few $billion here or there’. Meanwhile, all the middle-men and -women will not need to turn on their heating because their houses will be warmed enough just by rubbing their hands together watching the cash roll in.
(For reference, search for ‘US cannot account for trillions defence budget’. Estimates range from $1–21 trillion that the Pentagon has ‘lost’.)