I can see how the actual costume might be an issue for today's actors, though I've been on a few TV sets and can say they are often cold except when directly under the lights. Perhaps movie sets are similar, and it would actually be comfortable to wear something heavier.
In terms of a uniform, though, whenever this debate comes up, people want to assume the fabric would behave just like one today -- as though that must be wool because the costume is a wool. But this is supposed to be the future, with transparent aluminum and Retinax V. There's no reason to believe fabrics in that time period would have to behave like fabrics today. After all, we also watched them beam down to any number of environments on TOS just wearing the standard uniform. There must have been something adaptive in them.
I would like to point out, as a matter of discussion, that uniforms are also designed as much for their visual appeal as their material. The uniform provides a ready visual identifier of the person's rank, department and seniority within Starfleet, or other military type organization. Materials should be chosen that can adequately accommodate both the visual image and the work it is designed for.
As much as I like the TWOK uniforms, the officers jackets look too cumbersome for shipboard work. Even if the officers are just on the Bridge, sitting at their stations, and the materials are adaptive, in some way, they still look pretty heavy duty.
But, the idea of adaptive materials is an appealing one, but the visual impact has to be kept in mind too, if that makes sense.
From a strictly production point of view, the TWOK jacket was wool, so I would imagine that it was hot for the actors.