It can't be overstated how important this aspect of regular physical activity is. The feedback on your body's condition is priceless.
It's like the old adage "it's not a prison if you never try the door". You don't know you're unwell if you never try activities requiring fitness.
I think you might be missing the point entirely here.
You can "feel OK" when a whole lot is NOT OK if your daily existence is extremely sedentary and you never even move your joints through their full range of motion, let alone elevate your heart rate and break a proper sweat.
Exercise is literally about exercising your capabilities. If you don't exercise them, you don't discover they've gone missing until it's too late.