Another consideration is the style of writing. By the late '70s both the Marvel and DC universes had become comfortable and familiar places I was happy to visit several times a month. They shared a particular house style of art and, for the most part, had consistent editors who kept their respective universes pretty consistent. If a new neighbor moved in next to Steve Rogers, we knew about it and he was going to be there regardless of what title one was reading.
Today, the art and storytelling are wildly inconsistent, the details and characterizations are entirely unreliable, and each universe gets re-created every few years. Wolverine appears in most every title, and yet he may as well be a different character in each of those titles.
I don't buy comics anymore because my old universe isn't there anymore, and I see no percentage in getting to know a new one that has no internal rules and won't even be there in five years.