@SaganRitual As someone who went to a very good private grade school that taught well (including critical thinking), and who has known at least a fair number of teenagers who went to public grade schools who were also sharp, I wouldn’t say that being age 25, or being bashed around by living in the USA, are necessary to being a good juror.
That’s what I meant by “age by itself isn’t necessarily a problem” in my original answer.
But I think all of your concerns are potential problems.
The late-end cognitive development tends to be about moral thinking IIRC, so, that could be an issue for some people. But it’s not like everyone under the age of 25 is morally deficient.
The mostly-abysmal US public education system is a concern. But I don’t agree that living in the USA from ages 18–25 is necessarily going to teach most people a whole lot to make up for that.
Far too many Americans do lack fundamental critical thinking skills, and many have horrifying judgement and tons of anger bottled up waiting to project judgement on others. But again, I’m not sure that’s going to be less the case at 25+ than it was at 18.