I'm not sure about the uniform issue - but I guess the point here is that Starfleet is. If camouflage isn't going to work 100% or even 20%, perhaps it's tactically much preferable to be highly visible so that ground action can be coordinated? It's not for serious mental illness in the leadership that the armies of yore wore brightly colored coats: wearing dull grey or green might have meant defeat through loss of cohesion to units and, even more seriously, through total loss of IFF.
Timo Saloniemi
Visual identification is useful if you want to avoid civilian casualties. It is why uniforms and national identification are considered important in Western combat, and why non-uniform combatants can be executed in the field. That might not be a realistic system in Star Trek considering various alien nations can be brutal. I don't buy the reasoning for brightly colored uniforms being for coordination in the field, radios really defeat that reasoning.
It might be an assumption that camouflage is obsolete. Tricorders make camouflage obsolete, but then sensors trickery makes tricorders less effective, making visual identification useful once again. I wouldn't be surprised by camouflage, textile patterns, being a forgotten technology.
Not only that, I couldn't see why baldness still existed then. Picard wore it well, but I don't understand the Doctor's "horseshoe head" type of baldness. He complained about it more than once. As a hologram, he could have altered his appearance in any way he chose. And if he could stimulate Seven of Nine's hair follicles and give her a full head of hair after 18 years as a bald Borg, then he certainly could have done the same for any male crewmember with male pattern baldness.
The Doctor kind of liked complaining, and like you write, he could have changed his hair if he really wanted, it would have been trivial. I believe the notion we are supposed to accept is future humans don't care about appearances when those appearances are just a part of life. So, someone who is 100+ years old will just accept their age and the loose skin which comes with it. Picard went bald, and just accepted it as an unimportant part of his biology. Even the admiral in Insurrection didn't care about looking young, he wanted to be young, as in possess longer life, more vigor, and youthful strength.
At the same time, they get hair cuts, wear clean uniforms, and so on. They want to put forward a decent image since they respect themselves.