I agree on the youth thing. When I was younger I thought those season 3-7 uniforms were sharp. But somewhere along the way, they started to seem really out of place for people working on the edge of explored space in, possibly, hazardous conditions.
I think it really came into focus a few years ago when I was watching The Enemy. Watching it I realized those uniforms were really inappropriate for work in the field and likely a pain in the ass when someone on the ship had to actually work.
The only thing that seemed impractical to me was the zipper in the back. I used to always wonder how the heck they put those things on by themselves.
In all honesty "we're not supposed to see that" as it's not "really there" or if it IS there a design feature of the uniform not the "zipper." As we all know zippers are obsolete in the 24c, they have "nanoseam" closures the clasp the uniform shut int he front. This is very, very nicely demonstrated when Ro takes off her tunic in "Ensign Ro" (further suggesting that there's a "nanoseam" between the top and pant of the female uniform to make it look like one piece. Meaning the two-piece look of the male uniform is a design feature.)