This is highly regional - any major city with a decent transit system will have excellent bus routes in dense areas. Also, “operators” usually means bus drivers, not transit agencies

Only dense areas. Some cities are ignoring dense areas that other cities have proven can support great service because they are not the densest there. People have places to be, and large parts of any city do not have reasonable transit options even though the density is there. Too often you are foced to take the long trip downtown and then back out even though your destination is just barely beyond walking distance.

Am I misunderstanding you about the 15 minutes interval?

Every workday I take a one-seat King County Metro bus ride that lasts about 1 hr. The bus starts at a layover facility and ends at a different layover facility.

I don’t see how this 15 minute interval maps to my actual commute?

I don't think you're misunderstanding. I think the person you're responding to is misunderstanding that we were referring to trip end points (layover locations).

Very few people will accept commutes that long and so they are not something to optimize for.

(At least in King County Metro) their newer diesel-electric buses are series hybrids that use electric motors for traction, and diesel generators to power a small battery. The drivetrain seems smart but maybe other agencies use it less? You can look up the bus model online - New Flyer XDE class

(At least in King County Metro) the newer diesel-electric buses are series hybrids that use electric motors for traction, and diesel generators to power a small battery. So the low hanging fruit of electric traction was already “picked”. You can look up the bus model online - New Flyer XDE class