[watwut]

I don't think this is true. First, this is specifically not true about Witcher or Game of Thrones. Plenty of drama even if they all acted sensible.

Second, being fully grown adult does not have to imply perfection. Fully grown adults make bad insensible decisions all the time. They however do that differently then teenagers, for different more complex reasons.

And this is something that is super visible in Witcher. Original characters don't make sensible decisions all the time ... but they have adult psychology. Even when they are bad to each other, they still don't act like middle schoolers. They act like adults with issues. And show writing just completely stripped them off the adulthood.