I’d dispute this based on just one experience I had last summer. I’ve been flying non leading major airlines for the majority of my adult life. Think JetBlue then Virgin/Alaska. My family used to fly Continental, Delta, and going way back PanAm, but I like the upstarts because they usually offer more, and the service is more personal. Had to fly cross country to an event and want to fly direct from my closest airport and that meant flying American. I booked a business class seat, and the plane seemed old, dingy and used, the seatbacks didn’t even have video screens, even in the first class section, in the year 2023. So as far as that very non scientific, one experience, I can confidently say, they are not all the same.