I definitely understand your worry. There's not really too much too worry about though.
Going over the before/after, as well as where things are set, the red areas should not worry you too much. If you look at the small numbers at the top of the box in each area, this is the minimum and maximums. Toe is what usually will wear out tires the quickest. Having these with in the min/max range is the biggest deal.
On MANY vehicles, the caster/camber are preset due to how the suspension is built. When they are totally out of whack, something is usually worn out and needs replaced, such as the upper strut mount or one of the bushings in the lower part. The left front camber is a little out of spec, but really not that far. Seeing as though it had not changed at all from before/after the alignment means to me the technician was unable to do anything about it. IOW: There is no adjustment there. The technician is right about the rear as well: There usually aren't any adjustments to be had there.
Again, the toe on the right rear is "only" 3' of a degree out of spec. That is an infinitesimal amount and something you nor your tires will ever notice. If it was a degree or more, then I'd start looking for worn bits/pieces.
You'll notice the "total toe" in the front end, as well as the toe for left/right, all came into spec. This is good. Camber did change a little in the front end, but not by much. Caster didn't change at all. These are both good signs. If they did change a lot or came further out of spec, I would be worried more about if there were worn parts.
Again, I don't really see too much to be worried about. Believe me, if there were worn parts which needed replaced, the technician would have said something. They'd also have had a really hard time getting it aligned. As long as you are driving straight and it feels good, I think you're in fine shape.