Maybe we should ask ourself which if the X is problematic for board games.
eXplore: Cause issues if there is a random generation for the galaxy. Could give certain advantages to a player instead of another player.
eXpand: Seems to create a lag before the game actually start in the action. This is why most game's "actions" occurs in the last 2 turns when the game is over.
For example a game of eclipse should start on turn 7, because this is where the interesing stuff happens. At most the progresss could be accelerated by making those step in the setup phase and avoiding all the management of playing those phase.
eXtermination: This is generally the primary source of conflict, so it is hard to cut this. The biggest issue is player elimination which is not allowed in board games (or not recommented). Else other kinds of conflict needs to be introduced.
eXploit: This is basically resource management. It could be cut if you want to abstract the management of resources. But if you do so, you'll have to compensate with something else.