and you are somewhere in it
and it will never end until all ends.
Mary Oliver, "What Can I Say"
Like most Unquestioned Truths, this one does contain some, well, truth. The two main comic universes--Marvel and DC--started more than a generation ago. Since then, they've been expanding in all directions at once, and now, they encompass thousands of characters--from street level crime-fighters to cosmic entities--created by countless writers and artists. And nobody, no matter how many years they've spent steeped in comics' "arcane mythology," will ever know all of it. But that's not a weakness of the comics medium, that's an incredible strength.
To me, complaining that the comics universe is too vast is like complaining that a city has too many restaurants. Yes, you're going to eat at a bad one every once in awhile, but you're also going to find plenty of great ones. And if you have any spirit of adventure, you can stumble down a side street one day and find an Ethiopian barbecue joint you never new existed, and all at once you're in love with Ethiopian barbecue! Discoveries like that don't just make up for the occasional bad experience, they make life worth living.
I've been reading comics since I could read. In the decades since, I've found many creators and characters I love, both famous (Spider-Man, Batman) and fairly obscure (Firestar, Union Jack, Gunna Sijurvald.) There are old stories that I read again and again, and there's also always something new and interesting just over the horizon. I don't know everything about the Marvel or DC universes. I never will know everything no matter how much longer I read comics. That doesn't bug me. The thrill of comics is the thrill of exploration and discovery.
This isn't to say that comics don't have their flaws, just that the vastness of the shared, collaborative universes isn't one of them. In fact it's one thing comics do that no other medium has. Even an epic TV series like Lost or book series like Terry Pratchett's Discworld is relatively minuscule compared to the whole Marvel universe.
So, for comics fans and creators, stop apologizing for comics' sprawling nature or trying to "fix" it. Instead, embrace it as something that makes the medium unique. And for people wanting to get into comics but too intimidated, don't be. Grab a book that looks interesting and dive in! If you like it, follow that character or writer or artist to another book. If you don't, move on and try something new. Try Wikipedia or Comic Book Database if you're totally lost. But keep exploring, and before long, you'll find wonders you never dreamed were there.