I agree that it is ridiculous that there is nothing built yet. Me, personally,I don't visit the graves of my loved ones.I find no comfort and feel they are in my heart,not at the gravesite. That being said,if it gives someone else comfort,they have every right to have a say in where the remains are put.I remember visiting Ground Zero a couple years after the attack. It happened to be Fathers Day. I think it was one of the saddest thing I ever witnessed. There were people there who just wanted to mourn their fathers and could only stand around an ugly fence. I think it would be wrong for them to have to go into a museum for times like that,and something like the tomb of the unknown soldier would be more appropriate.
I can't think of any place I'd rather go for contemplation than a museum. Most museums are every bit as respectful as churches, but they aren't aligned with a specific theology.
Per the link, we're talking 50 complainants out the thousands of relatives of 9/11 victims. I don't believe any solution will ever please all survivors.