IIRC, director Nicholas Meyer had a lot of say-so in the costume design and overall art direction for TWOK
-- he wanted everything to have a traditional nautical flavor. The “monster maroons” looked fine as dress or parade uniforms, but they didn't seem terribly practical or comfortable for everday duty aboard a starship. And they gave me the feeling that the cast was about to break into a chorus of “76 Trombones” at any moment.
Pyjama uniforms are a must. Think about it - unlimited access to replicators and no TV? The crew would be as big as houses without those form-fitting uniforms and Dr McCoy's regular lypo-suction sessions.
The body-hugging uniforms that started with TNG are no problem, because in the 24th century, EVERYBODY has a great physique. Even middle-aged bald captains.