why it would not be enjoyable?
I think others have touched-on the degree of complexity involved in a game like GC2, and how it is quite difficult to make an AI to play it. This is not a case where brute-force "calculating moves ahead" gains you anything.
What makes playing a game like this "enjoyable" (for me anyway) is the idea that I have chosen a goal (a victory condition) and I make strategic and tactical choices to move toward that goal. To the degree that the computer players
appear to make the same sorts of choices (and tradeoffs) makes the game fun. In a game like this where there is no human-on-human play, it becomes even more important for there to be a computer player that
appears to play by the same rules that we do. If the computer is allowed to cheat, then it cannot be too obvious or our innate sense of fairness is violated and the game suffers. As we get better at the game, we start to notice that the AI doesn't fight very well, or doesn't defend against a specific strategy, or doesn't adapt very well to a specific map. Then, we start to handicap the computer player by giving it more to work with.
This is no different than veteran golf players giving their less skillful friends a few strokes to "make the game interesting." The statement that it is easy to beat Tiger Woods as long as my handicap is high enough is a close analogy to the quote in the original post.
Personally, I play GC2 to relax. I like to build a fleet that is a technological terror and rampage around the galaxy. That is fun for me. By the same token, I don't want the computer to be a total pushover either. So, I usually play at "Tough." On "Suicidal," it is highly unlikely that I would hold a tech advantage for much of the game, so that level would not be very fun for me even if I knew how to win under those conditions. Some people really get off on the "David vs. Goliath" thing. I admire that. But, that's not why I play. So, I don't play that way. YMMV.