I disagree. When a player is in the corner, he is being defended on two sides already. This allows the wing who covers the corner to overplay any return pass plus it limits the options for the offense. As well, with a third man free throw line extended instead of down low, the skip pass is more easily defended. In a 3-2 zone, the top three players move as a unit, with a slightly wider spacing. Any penetration between must be pinched by the defenders on either side of the attacker.
As for your point about 2-3 defending better in the corner, my problem with that has always been that on one side of the floor it will be a big man who has to close out an outside player. I assume you have played and you know that moving from the block out to the corner while playing a 2-3 zone is not an easy skill. When the match-up is the other team's best driver against a lumbering big man, the results are not great. On the other side of the court, with the small forward down low things are better. But I prefer to have my three best and quickest players defending on the perimeter.
I do agree with your first statement about the origins of playing zone. If a team couldn't its outside shots, pack all five guys in the key and get some rebounds. I think that zones have developed into more complete defenses. The 3-2 is an adaptation to keep rebounders down low but extend the range of the zone, and 1-3-1 goes even further, often including aggressive trapping in the corners and when a perimeter player loses his dribble.
Once I scored a basket that still makes me laugh.