It’s aimed at children, that’s what shonen anime is, the word literally means “boy”. For something aimed at an older demographic, you’ll want to search seinen. Consider “Monster”, which is something that could’ve been a western show for adults.
https://en.wikipedia.org/wiki/Gravity_Falls
Back to the seinen anime, Monster fits into the category of mystery/thriller. For science fiction/horror see Parasyte -the maxim- and for dark fantasy see Berserk.
https://en.wikipedia.org/wiki/Parasyte
https://en.wikipedia.org/wiki/Berserk_(manga)
Berserk in particular is a staple. It has influenced lots of other work.
https://en.wikipedia.org/wiki/Berserk_(manga)#Legacy
Be sure to not watch the 2016 anime series, as it is reviled for its poor animation. The 1997 anime series or the film trilogy from 2012 are a better use of your time. Both cover the same section of the story. However, be forewarned the part they adapt is a specific arc of the story near the beginning and is thus unfinished. Still worth it.
But I’d still recommend you start with Monster if you’re looking for something closer to live-action shows.
Yeah, this is one thing that I didn't like about AoT, especially in the first 4-5 episodes. Later I accepted it as its characteristic style, I think its strengths greatly overweigh this particular aspect. And, there is much more depth to the characters than the childish dialogs lead you to believe.