Just about the only innovations in board games per se that I've seen, that've made them easier to play, are increased focus on helpful iconography, and more widespread use of "cheat sheets" (cards, little cardboard bits with print on them) for each player. Not every game uses them, and not every game uses them well (the iconography, especially) but damn is it ever nice to sit down to a game you haven't touched in a year and find that just glancing over the player cheat-sheet and icons on the games' various bits is enough to refresh your memory of the rules well enough to present it to newbies again, leaving maybe just a few details of initial set-up to be looked up in the rulebook (and sometimes the really good ones sneak those onto the cheat sheets or graphic design of e.g. the board!)