In Prosperity there was one major exception - Monument. This card could gain points infinitely without causing the game to end. In practice, this never comes up because it's too slow compared to other point gaining options. Later, once cards could be gained out of the trash, an edge case entered with Bishop as well. First with monument, and later via a combo with Bishop, it's possible to gain points forever without actually ending the game.
Possible yes, best strategy, no.
Even in a Kingdom which includes Bishop and Fortress you will start to green someday if you are ahead in VPs. If you don't the game won't end and you won't win.
Many folks worry that cantrip VP token gainers could lead to infinte games but the same argument applies: if you are ahead in VPs you gotta start to green to win the game so the game will actually end. If it doesn't somebody is not intending to win which is plain stupid and doesn't require a rule change.
Empires is totally fine rulewise and actually significantaly opens up the strategic space of Dominion. In a normal game you gotta consider when to start buying Provinces, in alt-VP you gotta consider the relative strength of an alternative Victory card to Prosperity and in Empires you gotta potentially evaluate the strength of several sources of VPs.
Note that all official VP token gaining cards are precisely designed such that they don't work ad infinitum, Groundskeeper is tied to greening and Landmarks are either limited or reward you for having particular cards in your deck which will lead to a 3 pile ending.