I've found myself spending a lot of time lately praising the Intrepid class design, to the point where I'm starting to wonder: why? What is it about this class that makes a ship like Voyager more appealing to me than, say, an Enterprise-D or -E, or an Equinox or Prometheus?
One possibility is that I like the characters and/or stories of VOY more than I like the characters/stories of the other Star Trek series. Maybe... but for the moment let's assume that's not the case. What if there's something about their design that makes these ship classes distinctive?
As I got to thinking what it was that distinguished these ships from each other, I found myself fitting them into the three-fold model I imagine for Starfleet's charter responsibilities: diplomacy, scientific research, and the military defense of the Federation. Some classes seem specific to one of these jobs; some are capable in two; and a few classes are designed to accomplish all three needs.
So I thought it might be fun to rationalize this notion, to lay it out in detail and see whether it explains why I like Intrepids so much. If I'm onto something useful here, perhaps it will serve as inspiration for the development of new ship classes.
Right, then -- here's a first cut at categorizing some of the TOS+ canon Starfleet ship classes by designed role.
Hermes, Oberth, "Raven", Nova
Defiant, Sovereign, Prometheus
"GUNBOAT DIPLOMACY" (Diplomacy + Tactical)
Excelsior, Challenger, Steamrunner
EXPLORATION (Science + Tactical)
Miranda, New Orleans, Nebula, Intrepid
SOCIAL (Diplomacy + Science)
FLAGSHIP (Diplomacy + Science + Tactical)
Constitution, Ambassador, Galaxy
So how about this classification scheme of Starfleet ship roles? Does it makes any sense overall? How about which ships I've tentatively assigned to each role -- do those seem about right? Can anyone think of a starship class (i.e., not just a runabout) that is designed solely for Diplomacy?
Following this diplomacy/science/tactical breakdown and the four secondary role types I've derived from them, I see the Intrepid class as the latest iteration of Starfleet's exploration-focused designs. These exploration vessels are the ships that combine good firepower with science, but do without the support overhead of diplomatic facilities. The Intrepid class is thus distinguished from the Galaxy class by removing the requirement to house family members and civilians, thereby eliminating most of the Galaxy's capabilities for supporting diplomatic missions. (Of all canon Starfleet ships up to about 2380, nothing beats a Galaxy for its balanced effectiveness in all three of the primary starship roles needed by Starfleet.)
Additionally, the Intrepid class's use of folding pylons for the warp nacelles (to produce a warp field geometry that minimizes the damage to subspace caused by traveling faster than Warp 5) suggests that Intrepids are meant to spend a lot of time zipping around in deep space. Such maneuverability also supports the view that exploration is the primary mission for this class.
Dropping the support for diplomatic functions thus allows an Intrepid-class ship to focus on science and tactical ops. I don't know of any circa-2380 canon Starfleet ship class that better integrates just those two mission profiles in its design. The Defiant, Sovereign, and Prometheus classes are all much more focused on combat capability, while the Nova class is more science-specific. And although the Nebula has both science and tactical capabilities, from what I've read it seems focused more on science -- the Intrepid seems to offer a better balance between knowledge collection and firepower.
So in the end I see the Intrepid class as the paragon of Starfleet's exploration vessel designs up to around A.D. 2380.
And that's probably why I find the Intrepid class so appealing. Given that I'm a dedicated Explorer who not usually very social, a technologically modern ship like Voyager that's capable of discovering new things and living to tell the tale is exactly what I'd design for myself if I could!