I just thought I would chime in as the OP on this one. My River experiences and perceptions are 180 degrees opposed to the outcomes you have implied are predestined. I guess one could say, "one of the benefits of River cruising, especially with Viking, is that you really don't need to do any research about the destinations." Fun, huh?
One of the primary reasons I like River cruising (and viking specifically) is that one can build the framework of an incredibly active and compacted learning experience in to a very short number of days. By doing minimal research, I get to learn and experience things in real time as Viking curates a few hours for me; THEN I can spend the rest of the time in port on my own, diving deeper in to interesting things I may want to pursue, or have heard about, even if I have not "researched them" beforehand. In this manner, I have experienced things like EL DE Hause in Cologne, the Hospital in the Rock in Budapest, or that town's collection of Ruin Pubs, or even the most quaint local bier joint and it's Football fanatics in the town of Breisach.
Sometimes, you don't want to research 8 points on the curve .... but you sure enjoy experiencing them.
The information that ports may not be as accessible on an Ocean voyage is valuable however. It's good to understand the docking schedule and situation for every visited port, River or Ocean.
Side note, the Ocean sailing I lean toward seems to be port intensive, almost a upsized river cruise.