Firstly, everybody should realize that not all mangaka are exceptional artists. Essentially, they're drawing cartoons for a living, and some of them are no better at it than the cartoonists in your Sunday newspaper.
Secondly, as I stated, you have other more important details to worry about when your manga is a weekly serialized series. It's important to make prominent aspects of the panel stand out, not whether or not you've added detail to so-and-so's foot in the bottom-left area of that panel. And that's largely because the readers, on average, isn't going to care how detailed that foot is.
As for Lupin, that show came out in the 70's. Animation wasn't exactly at a pinnacle back then.