You certainly could spend a whole vacation at several of those places. But given you don't drive, I think you'd find the tour company would give you your money's worth. Places you've already been to would no doubt seem very rushed. But experiencing the others even in passing would be rewarding. Not being concerned about where to stay the nights is also a huge plus these days when many more people are trying to see the same sights.

When I was taking vacations from work, I got to drive to a rich area like Southeastern Utah (Canyonlands N.P., Arches N.P., Natural Bridges N.P.) and spend a few days going out from a single base. I got to do hikes at each place I didn't get to do with the family when I was a kid. But there is always more, hikes through parks that can take a week by themselves, and out of the way areas it takes time to drive to even if you have a car... You just have to enjoy what you can do. For instance at Monument Valley Park you can see much (the buttes seen in umpty western movies) from the parking lot, but to go into it, you have to go with a Navaho guide, and I never had time for that. Still glad I went.