Belgian here. Growing up, most of the stuff I watched on TV was either French or English (Belgian TV had little to offer at the time). There were no subtitles. I mamaged to pick up a good deal of French and a great deal of English in this way.
I think watching things in their original language is key. You pick up on things using context, some of which is lost in translation.
I've learned English the same way. A fair amount of people in my generation learned German the same way. It boiled down to which TV channels you had access to while you were a kid, and the lucky ones learned both.
As an adult, I have way less patience to stare at a screen and try picking up stuff that I don't understand. I've tried finding some Dutch shows with English subtitles, but it was shocking how little content I could find.
I think watching things in their original language is key. You pick up on things using context, some of which is lost in translation.