For me it depends. I tend to speak my mind, much to the chagrin of all you people.
I've definitely have some manga I'll praise, some I'll condemn, and some I defend. Ironically, usually I'm playing defense, but if something dumb happens, I'll criticize it. Which is why I still get shit for finding the ending of Gotoubon the fucking worse, but that's a can worms itself. (And no, it's not because [insert girl] lost.)
Honestly, certain criticisms are kinda overdone or dumb like "beta mc" or "used goods" which I feel are weak arguments themselves because they're more projecting standards onto the characters and not following how they are characterized in the manga. Good forbid you have had sex ONCE with an Ex or you're not exactly confident because you're a confused teenager.