The MCAS is there to stop the aircraft from stalling so why not call it a "stall avoidance system" ? If it walks like a duck and quacks like a duck, then it's a duck.
The B757 and B767 first flew 15 years after the B737 and are already out of production except for freighter and military versions of the B767.
The move from the B742 to B744 required an extensive redesign of the flight deck and systems, Boeing didn't just stick in a couple of TV screens in front of the pilots. The B737 should have had a similar in-depth redesign if they were going to continue with the same airframe, rather than the patchwork quilt of modifications and work arounds it ended up with.
It's a first generation jet modified into a third generation one.