This is Shatners 'Star Trek'

Shatner bought his version of Trek to the screen (bit similar to Gene Roddenberry bringing his version of Trek to the big screen with TMP, ironically Shatner adapted Roddenberrys oft desired 'Enterprise meets God' plot), hence why its fun, whimsical, comedic (partly a requirement by the studio after the blockbuster success of IV but also reflective of Shatner's personality), hyper feel/quick dialogue, action orientated, lots of running and jumping (as in action series TJ Hooker), Horses (also see Trek VII Generations), campfire (one might imagine Shatner in the mid 1970s campervaning out in the wilderness, campfires/singing), it all centres on kirk, and kirk being especially heroic (Captain Kirk climbing a mountain/why is he climbing a mountain, taking on the catwoman, holding out on Sybok, "I'm afraid of nothing", defeating 'god'/'what does god need with a starship?' The epic heroic stance against the Klingon BoP climax), Kirk seems more like Shatner in this than other films (more Captain Shatner than Captain Kirk - also see Generations*), poking fun at the supporting cast (Scotty bashing his head, Scotty & Uhura romance, Uhura naked dance, Chekov and Sulu lost/blizzard, Bones talking to himself/more wacky than usual, 3 Stooge element to the big 3), spock/nimoy kind of betraying him but not and ultimately saves kirk at the end (perhaps reflective of how Shatner saw their at times rivalry/friendship/relationship?)

*I mentioned Trek Generations a few times as there is several big similarities between the films and perhaps reflective of Shatners influence on the Kirk character as is portrayed in Generations being more Shatnerian (horses, very heroic/legendary, campfire/log cabin), and the film shares similarities plot wise (Sybok/Soran wanting to get to 'heaven' , the central characters under threat from being seduced by their memories, finale taking place on a rocky mountainous planet. deleted opening showing Kirks extreme sports/death defying stunt)