What does the number of combos have to do with anything? You cover the same corners on the track using the different circuit configurations. Your overall route might be different but the corners are still the same. The scenery is still the same. The immersion offered by that particular environment is still the same. We're better covered on the car front in terms of the variety available, and they all handle quite differently. But I have no desire to try all 900+ combos. FE3 in an LX4 is very much like FE3 in an LX6. KY2 in a RB4 is a very similar experience to KY2 in a XRT, bar the obvious handling differences. We might have hundreds of combos, but distil them down to groups of interesting/appropriate tracks and car classes, and the number drops dramatically.
No - personally, I want more content to provide more choice of racing venue, more variety, and yes, of course there is an appeal to having something new, both to learn and to play around in.
If everyone never wanted any new tracks, we'd all still be playing on LFS's recreations of the tracks from Pole Position on the Atari 2600. There's nothing wrong with wanting new tracks. It's not a sin. It's not symptomatic of having some kind of attention deficit disorder.
Mind you, none of this makes any difference if everyone continues to drive, and continues to be provided for/encouraged to drive, the same bloody AS3/GTR. I'd love to see what would happen if that combo could be blocked at the master server for a weekend.