>Domestic flights don't seem much faster or more comfortable than 10 years ago, and service has arguably gotten worse as usage has continued to increase.

It seems like this is a result of an industry "normalizing." Once something becomes mainstream the quality usually goes down but quantity goes up.

Sure the Concorde was innovative, but the ticket prices were extremely high. In the 80's IIRC a round trip ticket was $1000 from the US to the UK. Adjusting for inflation that's around $3k for a flight.

Taking a quick look....today you can get the same flight from 35 different carriers, little slower of course, but for around $600-1000. As much as people complain about leg room and amenities I think most people care more about price and availability.