A related thing that seems unthinkable for many people now is how dynamic opinions are. Like, not intelectually, but from experience understanding that my world view currently firmly stands on a foundation that might very well fall apart some day... I feel that experience deeply shaped my character. Funnily, I think my opinions are now standing on even firmer grounds since I stopped expecting them to hold forever.
People talk about their opinion as if it was some static thing that was always like this and will always be. Completely unaware how their own opinion evolved throughout their life and might evolve if they allow too. Also completely unaware of how irrelevant their opinion is, except for the consequences that follow from acting according to it.
"[...] But that's just my opinion. [...]", as if anybody should care. And, as if protecting their world view from the debate that might rip it apart. As if that'd be a painful and scary experience. (No even talking about how people use that sentence in order to spread fear, anger or hatred.) As if they'd need to put their whole life into question if they'd changed some if their opinions.
Often I think in the past there were people that lived according to this wisdom. I am not sure to what extend that's true, but I do not often meet such people now. Even in intelectual spheres, where some people even might talk about wisdom like this it often feels hollow to me if they do.