>I think the "open floor plan" trend is mostly to look impressive in photos and to get that "wow" factor when you first walk in. In practice, as commonly realized at least, it's terribly wasteful of space and makes houses feel smaller, because it's harder to get a wall between you and someone else, than it is in older houses.

I don't know. I live in an old house that I've incrementally opened up the first floor of. And I find the largely opened up space much airier and lighter and a generally better use of space than the more closed spaces were. That said, I do mostly live by myself so I don't really run into the issue of not being able to get away from other people unless I retreat to my office or small bedroom.