TOS has its essence--that which defined the series no matter the sub-genre of any particular episode. At its best, TOS' essence was the difference between having a story unfold as fantastic, or be some soulless, gadget-laden production, like most of Lost in Space. TMP rejected that essence in a vain attempt to be some eye-roll-inducing, would-be highbrow search for meaning. Chalk that up to Roddenberry, et al being hopelessly stuck in the pretensions of late 60's hippy / faux philosophers' inability to accept themselves, thus leading too many to fantasize that they "must" have some lofty purpose in the universe.
Those are subjective criticisms, though, and depend on execution as well as concept. What I mean is, what could one describe as "the essence" of Star Trek in 1978, in practical terms that could be applied to the new production? I think the idea of an essential "Star Trek-ness" was a much less-defined concept then than it was after several more movies, not to mention a new series or two.
I thought it was interesting that Meyer caught the Hornblower-in-Space vibe without knowing that Roddenberry was shooting for that (along with aspects of the western genre) with TOS. But he leaned on it a bit too heavily--too much Hornblower, not enough -in-Space.
I may be wrong, but my impression was that Meyer's "Hornblower" influence was pretty much exclusively from the Gregory Peck movie, not its literary origins.