I can make 2 points on both sides of the mileage story - both being "modern" vehicles.

1994 Chevy 3/4 ton extended cab 4x4 pickup; 454 ci TBI; 240 hp; 4-speed AOD tranny; 4.11 rear axle; 10,000 lb towing capacity. 10.5 mpg no matter what. But I commuted to work in this vehicle for many years for the following reasons:

1) It sat outside in Tornado Alley. Due to it's age, if it ever got hit by a hail storm (the biggest weather threat) I would get practically nothing for it from the insurance company. Because I bought it with very low mileage, I figured I better get the miles out of it.
2) Gas prices are traditionally pretty low in Oklahoma.
3) I carpooled. Thus I drove only 1 or 2 weeks a month.
4) I got even cheaper gas due to having a grocery store discount card. I believe it's 10 cents a gallon off for $100 of groceries.

Replacement for the truck above: 2019 BMW X3 AWD; 2.0 L Turbo 4 Cylinder; 250 hp; 8 speed auto tranny; Premium gas only; 4100 lbs weight; 4400 lb factory towing capacity. Accelerates better than my lighter, computer tweaked V6 Mustang and is knocking down 28 mpg so far. An example of modern vehicle engineering.