Where do you want to go? That should be the guiding force here. Then, after you narrow it down, come back read recent trip reports and ask questions. You will get answers.
The land trips are great. We did the Italy trip (Rome, Florence, Venice) even though it was a trip we could have totally done on our own. But the special touches are amazing - when I compare our Sistine Chapel experience with anyone else's, they are just speechless. I mean, we were in the Chapel for a half hour, while our guide talked to us about it, with just 40 people (our 34 member tour, three guides and 3 security officers). Compare to the normal experience - 5 minutes, no talking, with hundreds in a normal tour. (And we even got to take pictures, although that is not guaranteed.) And the fast passes to David and St. Mark's, etc. (Also a great trip for picky eating kids, as pasta, pizza and gelato are staples of the diet.)
We are going to try a river cruise next as that is what DD wants to do for her HS grad trip, but it will be a different experience just due to the size and number of guides. After that, looking at SE Asia and (post-virus, China), as they are not places I feel comfortable traveling on my own. (And hopefully Backstage Magic, at some point.)
But, if money and vacation time were unlimited, I'd also do the Rhone river cruise, Peru, Norway, Greece, Southern Italy, Germany, and South Africa.