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.