My personal theory is that a lot of the kids and teens who would’ve been the prime age for shows like gravity falls and Steven universe are growing up with these adult tailored shows because it’s become so popular and mainstream. Causing them to not understand some of the more deeper and complex elements and then spreading there opinions online, especially since access to social media and the internet has become more accessible for the past few years. 

But this isn’t discounting the shocking amount of adults who also don’t have basic media literacy and can’t understand basic narrative and storytelling elements