A further 757-300 restriction is in extended turnround time that has to be allowed because of the sheer time it takes to get all those passengers out and in through one door at the front, and down one aisle. If full on both sectors it takes for ever.
757-300 which sold like pork sausages in a synagogue
Like most of Boeing's recent stretches in the last 10-15 years. 737-900, 747-8, 757-300, 767-400. They seem to have lost their touch.