But set aside the mission. Bangkok has multiple targets that are quite fun, Colorado does too. Yet the complexity of the design beyond the mission for Bangkok isn’t too bad: the pathing is there, there are ways up there (disguises, actions, etc.), and it’s fine. Colorado? You have to more or less repeat the mission actions in every way.
Yes, if you look at it from a really simple point of view all of them are like that, but if you made a stalker contract it’s easier to get to him than Jordan (having a hard story target is fine, really). But if you mark out almost anyone in Colorado you have to go through the same steps you would for a story target – the other areas are just as non-viable as the main.
Sapienza, Marrakesh, and Paris, are all like Bangkok: the choice is wider. Colorado isn’t a difficult mission, it’s a level with needless patches of linear behaviour which could have been overcome by tweaking a few things. Sadly, tweaking the wrong things would oversimplify other levels, just as tweaking towards it could (has?) hurt them.
(Hell, the training missions are less linear than Colorado.)