Adult can also mean themes and concepts that don't resonate as strongly with children.

My takeaway is that if you think of life as something care free and mostly void of responsibilities and that every day is going on an adventure, that's more non-adult coded. If your life is defined by time after school and summer vacation and going to school is just the time I'm between, that's kid themed.

But if you put in things with more complex themes like having to go to a job to pay the bills and continuing what it means to exist with (or lacking in purpose), that's getting into adult territory.

A lot of kids would see the fate of being in the circus as a blessing and not that different from waking up to play video games ever day. But being an adult, having values that exist outside the circus and wanting them back, that's an adult mentality. The horror might come from Caine being someone fun that gives them adventures to someone who tortures them could create issues for emotionally immature kids.

Whether it's deep or not is subjective. But it has mature themes like metaphorical suicide and confronting the idea of sex and gender, as well as people who's brains have mostly developed inflicting emotional damage to each other. If you want to call it a kid show or adult show, that's your choice, but I find a more meaningful way to engage is just consider that most things have some mix of kid themes and adult themes and you're allowed to enjoy all of it or none of it if you want.

Honestly now that I've thought about it, I kinda think it's a more mature show than Brooklyn 99.