It isn't even "proper fanboyism". It's just tribialism at its purest state. People wanting for their side to win over the other (In this case the MCU) by defending this movies at all cost. That cost of course includes character development, coherent plot, pacing and editing, overall tone of the movie, etc.
A "proper" DC fanboy would probably be more concerned about how their beloved characters are being portrayed and the stories being told in this big blockbusters. They would be concerned about how the DCEU deviates from the identity and core of these superheroes, but apparently these new fanboys are more concerned about how cool some action scenes look and the kick ass soundtrack so they take WB's direction as the right one when it comes to superheroes movies.
At the end, you get what you get. Murderman, Superman being more insecure than a teenager, an autistic lex, Critical panning, suboptimal box office performances and a bunch of people saying that everyone is against DC movies.