What makes a good map for me is: variety and commitment to rotation.
Rotations: If you hold short on d2 it takes you 0.1 sec to drop down to watch mid but then if you want to come back to watch short it's very risky running through ramp if you don't have long and also takes like 10 seconds. Same with overpass balcony, nuke vents. This makes your decisions as CT very important. Whole round can hinge on how you react to the info you get from the map. Fakes from Ts are much more potent cos once you fall for a fake you can't go back on your decision very easily.
Variety: overpass allows both aggressive and passive defense from CTs. Same with maps like mirage, you can give up A and play retake if you have mid or palace. Maps like vertigo or old cobble are boring to watch cos CTs don't have aggressive options.
Having long, short, tunnel, T spawn to mid doors sight
Ability for ct aggression, makes overpass so good
Perfect map is a map of the real world after you uninstall this crap game.
That it looks like mirage
I don't think a map necessarily needs to be balanced 50/50 to be a good map - nor does 50/50 balance necessarily make it a good map.
I agree with the rest of your points though.
It needs good gameplay (which is subjective), but it also needs to be simple - at least in layout. The first iterations of overpass and vertigo were significantly worse than their current versions because of how unnecessarily complex they were. I think vertigo still has room to improve, but overpass is one of my favorite maps atm.
The visuals in terms of contrast, like you said, should be good but that's an easily solved issue. Valve has put white-ish backgrounds in positions that are harder to see throughout the years to improve visibility. I don't find the overall theme of the map that important, but many disagree.
The smoke thing is an interesting point. I wouldn't mind if more parts of certain maps required more than 1 smoke to have perfect cover. For example, I don't think it's worse that you need two smokes to cross long (unless you smoke CT spawn). Obviously, an overwhelming majority of chokes are designed with 1 smoke/molly to be able to contain that point at the moment.
50/50 winrate not necessarily good
maps need to be interesting and not too complex
visibility is important, theme less-so
i don't mind 2x smokes to block a choke, but 1 is the current standard
The "balance" part is not that important, as SpunJ once said, it is nice to have some maps ct or t sided. I would go as far to say that best map should have 10ct:5t halves. That will cause menatlly weak teams to suffer but strong teams will show their dominance.