Just using them as examples there are many other Trek episodes that have absolutely nothing to do with Trekking through the stars. Be it time travel stories, to episodes onboard the ship that are utterly not connected to trekking through the stars (like The Drumhead), to episodes like Family.As a kid I never saw the appeal of either VH or CoEF. Even as an adult I intellectually acknowledge their success but don't tend to rewatch them. Them being extremely popular is one of those things that I just accept as given without actually feeling to be blunt, unlike say, First Contact or DS9's later Dominion Wars episodes which I genuinely enjoy.
Now using Voyage Home as an example, its one story and its the only story we are getting for nearly 2 years, and its primary setting is the past. At least now with serialized story telling, if we have. story that is primarily set at one place (in this case the past), we still have access to new Trek that offers the chance of material in a different setting. I would be more bothered if the shows overall concept was a time travel adventure that lasted for almost the entire run of the show.....