You knew perfectly well that the MCC was a huge exploit
The only thing about the MCC being a huge exploit is that it was not properly documented. However after 3 years *everyone* was apparently cognizant of the fact except perhaps the developers.
Why is an in-game economic bonus an exploit in and of itself. Simply the fact that it was a 100% bonus, perhaps. But otherwise it required a reasonably high level of tech to be researched and a reasonably expensive wonder to be built. There are literally dozens of similar although smaller bonuses for morale, social and military production and research. Why not an economic bonus.
This issue is two fold. One is the magnitude of the bonus and the other is that the bonus wasn't intended. One could certainly argue that 100% may be too much, however one cannot argue that an economic bonus has no place in the game whatsoever. One can also argue that functions should work as described so that everyone knows what is truly available however this doesn't mean that a well-known bug that has existed for at least three years should be nuked.
As far as fixing the MCC to do what was intended, who in their right mind believes that will ever happen. The best is that the MCC will become totally devoid of function and merely add to the already long list of useless techs and wonders in this game.
How were Stardock not aware of this bug?
This is the 64 thousand dollar question. It was the same question that was asked when the 5% morale bonus was removed from the Stock Market.
It kind of makes you wonder if any of the developers have ever even played this game. In their defense it's clear that they have played this game it's just that they tend to play short games on tiny galaxies that barely scratch the surface of game functionality.
Now if your talking about exploits why not take a close look at diplomacy in this game. Isn't it a huge exploit to be able to go 8 months into the game letting the AI's colonize the galaxy and then go to each AI in turn and say "Please give me all your planets" and have each and every AI say "Sure, no problem". The MCC pales in comparison.