This was a staple of my TV-watching when I was growing up; a lighthearted sitcom would take on an important social issue of the day, such as racism or alcoholism.
Honestly, I can’t think of any such thing happening on any TV show I watch nowadays. Mike & Molly is basically one long running joke about eating disorders (with some jabs at alcoholism and drug abuse thrown in), but there doesn’t seem to be a moral being preached. The Big Bang Theory has somewhat exposed the problems resulting from bullying, but does not seem to hammer on the issue.
Have you seen a VSE of a show you watch?