Lots of thoughts on this. I think that before you can neutralize a player’s economy you must capture all of their victory cities. Frankly since I play rarely and never online we usually play for capitals anyway and ignore VCs except for a few recent games with new players I’m trying to teach OOB.
As for second Capitals, I’m all for it. I really don’t care for games where minor victory is a winning condition. The whole point of the war was domination of an ideology, submission of foes, or unconditional surrender.