It actually kinda is game over; it's just the AI is too stupid to take advantage of it.
I guess you could protect your city, but you have no way of stopping the enemy from pillaging everything and they can stop you from expanding a lot easier than you can stop them. And it only snowballs as tech levels increase.
I mean sure you could have a civ with a combat advantage and rainforest hills surrounding your locations but in most cases I just can't see how you could win against an opponent that's even mildly interested in winning.
I think these things become readily apparent when the AI does take advantage of the unfair situation like say Montezuma is right next to you and attacks with 6 eagles. Even if you survive, your opening is completely hosed. And opening slingers would have been an autoloss.
And they've only recently changed the AI so it can take cities. If it ever learns to actually play, I'd imagine there would be more unwinnable situations if they keep this level of bonus.
That being said, IMO, without balanced resources, a game should not be considered a competitive one.