Drivability is pure speculation at best. It is wholly subjective.
It's means very little when someone says such and such is undrivable. That is THEIR opinion and nothing more, although some treat their own words as written in stone.
Exactly. My 4 banger econobox cruises in 5th at 4500-4800rpm, doesn't bother me a bit. My busted *** old suv feels like I'm taxing it if I cruise over 2800rpm. My Dart annoys me over 3500 rpm and when I honestly assess this "driveability" metric it really only comes down to noise and harshness.
The econobox damps some of the unpleasantness of turning so many revs where the suv is likely designed to make you avoid higher speeds/revs (3k in OD is about 85).
My Dart is only annoying because of the flow/drone masters. With the efi, I programmed in a bit more idle valve open when at cruise, this helps reduce engine braking when easing off the throttle and completely changes how "taxed" the engine feels at 4200rpm on the highway (3.91 gears and 25" tires..).
Getting the tuneup right also helps a ton. A lack of timing will make the engine run hot and take a ton more pedal to hold speed up a hill and make a ton more noise. With proper load/no-load timing it just drives like any other car.