(3) I'd agree that TNG is "genuine sci-fi" (although I'd drop "genuine" as being redundant; it's either sci-fi or it isn't), but I'd also argue that the later series were just as much science fiction as much as TNG was.
I think what muddied the water in regards to the sc-fi aspect of TNG are (to me at least)
- The A and B plots confused the 'serious' plot
- The lack of wonder at most any great discovery - eg. Picard seemed to have more interesting things to do than marvel at the Enterprise going to the Andromeda Galaxy
- The lack of Classical Science Fiction themes but more modern ones such as cloning etc
- The political plots involving the Klingons etc