You forget hard work.
Usually the reason I fail at late game is that I don't have the stomach for microing everything. Best late game guys are the ones with early game just strong enough, who are nice enough not to get ganged mid-game and who have invested enough time to be a late-game power.
Mind you, there have been quite creative builds even in this game, but some things fail and succeed depending on their environment.
And while you are spot on about experience and situational advantage, people usually don't consistently " just get lucky".
