In reply to Innovation:
You have two questions and there are two different answers...
To be successful, a game must stand out in comparison to its competition. Having a new mechanic helps but is not strictly necessary. However, the successful game must do something to distinguish itself... Either mechanically, thematically or with components or technology.
To be good, a game does not need to be innovative in Any category, just above average in most all of them.
And yes, somewhere around once every other year or two we add some new mechanic... Deckbuilding being the last one.