honestly, it's just that the mc has brainrot. You wouldn't call a person a mob or a npc if you didn't have some kinda brainrot from being online too much or something. Dude just means normal or inconspicuous, which means to just not be an asshole. Thing is, from what I'm getting from glancing at the novel, there's some extra expectations for him being the heir of a duke. That or some combination of the author never meeting a kid in real life or the mc transferring his impression from all the bad shit he would do later in the game to more innocuous stuff he does as a kid.Trying to be a mob is quite retarded, just don't be an asshole like in the original work.
Like, my sister is a 'boy mom' with a bunch of daugthers and her youngest being the lone son. If he did that shit where he needed a woman to hold his hand everywhere, she and her daughters would be fighting eachother to be the one while I would just glare at him and threaten an ass-whoopin if he starts throwing a tantrum about it. Right now, mc's at an age where his behavior is split between cute and annoying depending on if you're the same gender or not. (another thing authors might forget. Women, especially older ones would probably just see the boy's behavior as 'cute' or 'funny' the way a man might see a little girl asking to be carried around by a strong or attractive guy as the same.) You'd expect the parents to straighten him out but it's not worth calling him scum yet.
That said, I'm talking about what he's done so far, not what he would have done later. And to bring it back to 'just don't be an asshole', seems like the maids, soldiers, and everyone already look down on him even for his current, more mild behavior, which, as I pointed out, seems weird to me.