I am on record as a fan of the TMP uniforms when this subject has come up before. To me, it has nothing to do with how they look, but how they work conceptually, and the TMP wardrobe is the highest concept in all of Trek. Having different choices of uniform styles and colors on a long space voyage does seem like a futuristic concept, as well as being more semi-civilian or para-military rather than like a traditional military service as we know today. And think of how popular short sleeved shirts are, their inclusion in TMP seem more likely to me than their exclusion in the rest of Trek (OK, McCoy had a set for sickbay wear).
I don't think that the TMP stuff was perfect, either. I don't like the "shirt tail" cut at the bottom of the tunics, for instance. I like the idea of the shoulder rank in TMP, but it was pretty hard to see except at close range, something a little larger would be more useful. But that's just personal opinion, it doesn't take away from the overall concept.
The color palette of the TMP uniforms may look a little drab to some, however it was rather stylish at the time. The subdued tones remind me of the stuff Halston was designing for Braniff International Airways around that time:
Fashion trends change.
Do the TMP uniforms look like pajamas? Maybe they do today, but what has that got to do with guessing at the future? Here is an image I posted in a similar earlier thread:
Would someone in the 1860s be able to guess that the two photos are the exact same type: US Navy admirals and their staffs? Or might they think that the lower photo looks like laborers, or some kind of sportsmen, or men standing around in their pajamas?
As for the TWOK maroons, I don't like them, but again not because of how they look. They just represent such a radical break with Starfleet's established uniforms that they are not credible to me. Unless there was a major "cultural revolution" between TMP and TWOK, I guess.