Nostalgia aside, that Linda Carter series was dreadful. And outside of Super-Friends there haven't been any WW cartoon interpretations that I would consider light-hearted. The JLU character showed some humor in certain instances but she wasn't "light-hearted". And the WW animated film also isn't something I would call light-hearted.
Also Man of Steel was inspired by Mark Waid's limited series Superman: Birthright.
I enjoyed the Linda Carter series. It was fun and funny with a charismatic lead. The Justice League cartoon on Netflix is not some deadly serious fair. It is light hearted IMO. And like you said Super friends was light hearted and I loved it.
I think making super heroes ‘serious’ and ‘philosophical’ is liming your audience. Most kids are not interested in that and adults who are not diehard fans don’t want that either. They want something fun that they might actually be able to take their kids to. You are really just limiting the audience to comic nerds when you go the serious/angsty route.
Maybe Man of Steel was but this upcoming movie featuring Wonderwoman isn't. Zack Snyder has said, the script for Batman V Superman: Dawn of Justice is a script that was made up in a room with the minds of the creators of this movie throwing ideas around and creating a fully realized story.