Angela Lansbury always said the advertisers never understood the demographics of the people watching MSW, and I think there is a lot of truth to that. It was a very broad appealing show, it wasn't just "old people" or "grandparents" watching that show, it was entire families and a generation of kids who grew up watching it with the elders in the house.
To this day, MSW has remained a fixture in global syndication, it's bound to be playing in almost any country you visit in the world somewhere. That cannot be said for those big/glossy primetime soaps (which I liked as well when they weren't too stupid), they just don't have the same type of longevity.