There's nothing more tedious than voice-over work. It doesn't even really feel like acting, compared to how they worked on the TV show.
There was plenty of looped dialogue in TOS. Just about every scene shot outdoors had its dialogue completely re-recorded, as is normal in Hollywood because of the difficulty of capturing good audio on voices when there's plenty of unpredictable environmental noise around, or because of the need to cover the sounds of passing aircraft or trucks (not something you'd want to be audible on an alien planet). Pretty much all the dialogue in TOS's outdoor scenes has that distinctive "standing in front of a mike in a recording studio" sound, since they weren't as good at faking an outdoor ambience then as they are now.
See also Bilar in "Return of the Archons." Part of the reason his performance is so creepy is because it was dubbed by a voiceover actor (possibly Walker Edmiston) and has that stilted, studio-recorded sound. Since all his scenes were outdoors and therefore 100% of his dialogue had to be looped anyway, it was simpler to use an available voice actor than to bring Lev Maurer back in to dub the role.
And good voiceover acting absolutely
is acting, and many terrific actors have made names for themselves with their superb voice acting, like Kevin Conroy, Mark Hamill, Tara Strong, Jennifer Hale, Kevin Michael Richardson, etc. It's just a matter of having a good voice director and the time and training to do it properly. Heck, I can name at least two notable actors -- Michael Dorn and Morena Baccarin -- who, in my opinion, didn't really become good actors
until they took up animation work and learned how to use their voices expressively.
Another interesting observation to take note of, is that one of the failings of the animated series they'd done a few years earlier, besides the mediocre animation itself, was the lackluster voice performances, which were similarly wooden & lacking in dynamic compared to the show, & performed by many of those same uninterested actors. I think maybe those guys weren't all that good in the sound booth back in those days
The veteran voice performers in the cast -- Doohan, Takei, Barrett, and Nichols (with her singing and stage experience) -- did better at it than Shatner, Nimoy, and Kelley. And Shatner managed to up his voice-acting game considerably in the 6 episodes of the second season, perhaps because production was less rushed, or perhaps because they had a different director that season.
Wise may have directed a lot more fllms than Kubrick, but he's rarely mentioned in the same breath with him. Kubrick was obsessively meticulous, that's why he made so few films comparatively.
The point is not to start some silly argument about which director is better. The point is simply that it seems naive to assume that the only reason Wise made the directorial choices he did was because he was imitating Kubrick. Wise had decades of directing experience that significantly predated Kubrick's work, so he was probably drawing on his own reservoir of experience. As evidenced by the similarities of TMP to Wise's own
The Andromeda Strain, and perhaps even in some ways to
The Day the Earth Stood Still with its cool, intellectual hero (though that's probably stretching the point).