It's a notorious issue with practically all famous long running cape comics and one of the highest walls people need to overcome when they want to give the comics a chance. Also one reason why the constant relaunches are the perfect "jumping off point" as many like to joke, because they just make an allready messy situation all the more worse.
I think two good ways to handle this issue are to either have people who can point someone into the right direction to read up on the history or have the mentality to just roll with it and try to piece the old events together by hints and remarks made in story.