As a comic book fan, I'm well acquainted with continuity. No matter how many times Marvel or DC re-sets the clock back to zero, fifty some-odd years of history still remains. All those stories are informing the present. Even if the publisher has decided to retcon everything, that history is still influencing the people behind the scenes. They're consciously deciding whether to embrace or reject all that came before.
Having said all that, it's not impossible to jump into a long-running series. If the creative team is solid, the story should still be as engaging and compelling for a new reader as an old fan. Done right, all that history will give palpable weight to the present. The newbie might not know the specifics, but they will be able to feel it. And once you've hooked them, they're certain to go searching through the back issues.