If you do more than is expected of you then people will expect more of you. For a time, these additional responsibilities will come with pay increases but after a while the responsibilities will grow at a faster rate than the paycheck. If you ever grow tired of these "additional responsibilities" it will be difficult for you to get back to your usual responsibilities at that company. Your "Quiet Quitting" may turn out to be a regular quitting in favor of a position, with regular responsibilities, at another company.
It almost seems like work doesn't adapt well to changing situations. In your younger years, you may of had bigger ambitions than you do now but your employers expectations will remain the same.
Is Quiet Quitting a bad thing?
If Quiet Quitting means that you no longer feel like going beyond your core responsibilities than I wouldn't consider this a bad thing as you're doing what you were hired to do. Anything else you might of done, like helping other departments or staying later, was a bonus - a bonus that you no longer feel like you can do.