The short answer seems to be no. Newer planes are much more efficient than older ones, but the most efficient aircraft and flight segment per passenger-distance are the A320 Neo and 737 Max making ~1000 mile flights.
Fuel burn is probably not the main reason airlines use the routing that they do.
I'd guess that staffing and gate time are big cost drivers. A lot of those "how Southwest succeeded" articles from back in the day cited very fast gate turnarounds as being a key thing— get the people off, get the other people on, get back in the air.
Fuel burn is probably not the main reason airlines use the routing that they do.
https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft