Maybe some people have a certain disdain for the CBS seasons because apparently people don’t like the 70s and obsess over the 80s. I on the other hand have always been fascinated by the 70s. Maybe at the time it wasn’t that interesting, since it was just a contemporary setting, but now it’s as much of a vintage throwback for me as WWII. So I think the 70s era of the show actually might have improved over time due to the nostalgia factor, for me. Also I have seen various others 70s shows and Wonder Woman actually looks very classy in comparison IMO.
As for the villains, there are some costumed villains in the show, even if they are original characters. But keeping things grounded was just the trend of the time. Even Superman 1978 was very down to Earth when it comes to Lex in comparison to Batman 1966 for instance.
The Incredible Hulk followed that line of thought to an even greater degree.