Yeah, all of this is so true. Even a loaded Civic has stuff like heated rear seats. Those were only luxury car features a few years ago.
The Mazda 6 looks like a much more expensive car.
"Shifting the goalposts" so to speak has been a continuous thing in the luxury car market for ages, and let's face it it's hard to avoid as technology becomes more advanced.
I think back to something like the 1960s Lincoln Continentals, which I think would be hard to argue were NOT luxury cars. Back then, paying for a luxury car got you:
1. Air conditioning(you pretty much have to custom order a car without it now)
2. Standard automatic transmission(once again, pretty much the only thing without an automatic now is either a sports-oriented car or an ordered low end model)
3. A really big, freaking huge engine(who cares about the cost of gas when it's $.10/gallon and you're spending that much on the car, plus you want loads of torque so you can cruise down the interstate in your boat with no effort)
4. Power windows-again hard to NOT find now
5. On the convertible versions, a powered convertible top(few convertibles don't have that now)
There were a bunch of little things, but those are the ones that come to mind.
Fast forward 20-30 years, and now all of the above is pretty widely standard equipment. A luxury car gets you heated powered seats and maybe something like a basic trip computer.
10 years ago, you started getting electronic infotainment systems, and again those are making their way into low end cars.