Seeing the brand names you cited, I’ll assume you’re in the US, so my comment may or may not be as useful as some brands are way different in France (for example, Subway is decent most of the time).
Growing up I sure got less and less attracted to fast food, and trying it occasionally did feel bad in some case. Although there’s a definite shift in not wanting to clog my own arteries, it’s not all there is to it. Some brands really feel awful now (McDonald’s being the worst fast food out there these days), but there are also other that still “hit that spot” (BK mostly). I think it’s safe to say that some big names let themselves go bad, AND it is still possible to find good fast food stuff.
With that said, it do gets more expensive, as everything else. The craving for fast food really become less common as time pass, and although it’s still good while eating, there’s still a tinge of guilt afterward, knowing it’s both too expensive for what it is (I mean the actual food, not necessarily that it’s too expensive for service and stuff) and that it’s not that great for yourself.
I’d say if you keep them as an occasional treat and know a few good places to indulge, it can work. But it sure feels like it requires more thinking than just dropping in any fast food joint to have a good time.
Businesses tend to follow local laws, even outside China.