Passenger aircraft are optimised for a maximum passenger load (plus baggage), so there is not much cargo space left with a full pax load, 3-5 tonnes at most.
As with all sweeping generalisations you are not entirely correct.
I listened to a presentation by Rod Eddington where he talked about why he loved the B777. He directly contradicted some of your assertions.
But then he was only the CEO of a large and successful airline so what did he know?