Some heavily-defended islands were bypassed.
Iwo, however, was taken because we needed Iwo Jima as an emergency airfield for B-29's that were damaged over the Empire and couldn't make it back to Saipan and Tinian.
Roughly 2000 B-29's (carrying 20,000 crewmen) landed at Iwo.
So you're saying the attack was a good idea, and the top flag officers deserve credit, not blame, for how it turned out? I'm no big-time expert, so I suppose you may be right.
General MacArthur was known for bypassing the most heavily defended islands. The Navy and Marine Corps were known for the opposite approach -- and they sure payed a huge price.
I think I meant to type "paid," but my brain isn't working right today.