You still have to guard guys who can hit 3s. You have a choice, 1) you help down farther off the guy and your close out is a foot longer or 2) you don’t help and stay attached to your man which creates a gap a foot bigger.You seem to be suggesting that offenses will be better because we move the 3pt out or am I missing something? If that were the case, wouldn't teams have figured that out already and just be doing that anyway.
It doesn’t matter what teams did before. Assuming the offense uses the 3 point line as a measure of spacing, closing out to the old 3 point line was closer than what the new one will be. You are forced to show your defensive priorities a bit more as you choose which areas to cover.