Given how much cheaper the U.S. has become, no change in the number of visitors reflects a general loss of interest in visiting. With the dollar worth so much less than in 2000, the number of visitors should be breaking all records. Of course, this is not just due to the consulate policies, but also to horror stories of treatment by immigration authorities, and so on.

pre-visit appointment system

A good idea in principle. In practice? Well, in Germany, it used to be (still is?) bookable only on a 900-equivalent number which left you on hold a long time. Maybe a good way for the State Department to make money, but not a good way to make the U.S. popular...

Yes, I suppose you are correct  in saying it is possible that they could be searched and allowed inside, but it would seem to be much easier just to not bring them in the first place.

If you're coming by train from the other end of the country,  you're supposed to bring nothing with you? Regardless of how many people visit the consulate, if they can handle those people once inside, they should be able to do a security check as well. Unless processing the application is significantly shorter than the security check, in which case one wonders why they have to come to the consulate at all.

Probably my last word on the matter, as I'll have limited internet access for the next week.