The difference between the older, more detailed figures, and these new ones, are that the previous versions were based on movies, while these are based on comics/the upcoming game. I'm not trying to argue a point, your opinion about how you feel on the arm/leg printing debate is your own, but a lot of the time it really just seems that the material a figure is based on just doesn't need a load of detailing to keep up with a track record of leg printing.
*The legs on Captain America have never stood out as something that needed printing, whereas Doctor Strange has a much more interesting outfit which would benefit from leg printing. So really it's just easier and cheaper to use plain legs than create new printed legs for Captain America which are just a couple of lines.
*Black Panther in CW had a lot of silver detailing atop his head, hence the printing on his ear piece, but his BP costume didn't have the same type of detailing, hence why it would've been left plain.
*Hawkeyes previous figures have always been based on the movies, which have quite a lot of detailing around his legs, but this new one is comic/cartoon based, which doesn't have the same type of leg detailing, thus not exactly needing any leg printing
IMO we all expect so much from the theme, but it's all more than we need. Characters with extreme levels of detailing will more than likely get it, but not everyone NEEDS that level of detailing. It's not because LEGO is lazy, or don't care about keeping up with keeping the same level of quality, it's just because not every figure needs the same amount of detailing
Many themes have introduced pieces that are designed to be exclusive to only one character, the number of these parts have grown over recent years with themes like Overwatch, Minecraft, Powerpuff Girls, but Marvel have plenty of pieces that couldn't be used outside the theme, just for a couple examples, Iron Man's helmet, Loki's helmet, Magneto's helmet, Star Lord's mask, all 3 iterations of Groot, MODOKs head, etc.