??? shit take alert
Goblin slayer, (the first few episodes of) Shield Hero, Cowboy Bebop, A Silent Voice, etc
Just because its a cartoon doesnt mean its for kids. Think Invincible, for example. Even then, most of Invincibles (and Goblin Slayers) non-child factor comes from the gore, which isnt necessarily the only way to make a show not for kids. The early parts of Shield Hero deal with betrayal and false rape accusations. Cowboy Bebop deals with a lot of the characters feelings when theyre not leading up to or doing a fight scene, and is pretty adult with the concepts in portrays with drugs, morality, etc. And as much as i advocate that Your Name is better than A Silent Voice, A Silent Voice is much more adult in its themes. Attempted suicides, redemption, "earning" forgiveness, forgiving yourself, etc.
Of course if you just watch shonen anime youre just going to get stuff for younger people. Its supposed to be exciting, not deep. That doesnt mean you cant enjoy it, though. Plenty of other people prove that. One Piece, Dragonball, etc are so loved because theyre good enough to stay popular with their original fanbase and theyre able to pick up new fans. These shows are supposed to be fun, exciting, or whatever you want. If you think you cant enjoy a show because its exciting and "made for kids", you're still a child LARPing as an adult.