It's not an excuse, it's the truth, which can be exhibited by the number of changes/revisions the game is still undergoing. And it will be no longer true once the game enters beta testing and/or is released as Gold. There is no time limit placed on Alpha status. There's no magic formula that says after 'x' months your game is no longer alpha and you have to release it as it is.But at what point is the excuse "it's just a alpha" going to quit being used? 10-20 years from now???
If the game were static and no longer receiving updates, then your premise that it is no longer an Alpha game would be valid. There are games sitting in "Alpha" status on Steam that haven't had an update in years. However, when a game is undergoing constant revisions, then that definitely qualifies for Alpha status. At least in my 'group think' mind.