@Liquidxlax
If a manga has someone get assassinated by a fleet of isekai trucks and suplex dragons, I really can't imagine someone would take issue with that being called dumb - at least in some respect.
It's a tongue in cheek kind of dumb and it puts effort into the context and justification as it goes. Or in other words: it's a dumb premise that plays out seriously, but still ends up being kinda absurd in a way that sounds dumb on paper. See also: most of Jojo's Bizarre Adventure.
Plus "dumb" can mean a lot of different things anyway, it's weird that you're speaking with such certainty on it. Consider even when Simpsons was sensible there were still aspects of it that were dumb, or at the very least silly (which can be construed as dumb), by intent.
When you talk about a written fictional work, the elements involved in a given plot or scenario can be "dumb" or nonsensical by themselves, while the context and execution for them are clever. Which again, just means you have to specify what exactly you mean by"dumb"