I just want to say that "It's a cartoon but seems like it's not for kids." is a weird stance since animation aimed towards adults has been a thing for a very long time. Maybe even longer if you look outside of American animation as anime has had that since at least the 1990s. I know you probably didn't mean anything by it though, but just saying.

That being said, taking a previously long established children's series and then turning into an adult aimed one IS rather weird and maybe tonally inconsistent to all the previous iterations, but also maybe not the first time that's happened.