If you think someone should be barred from participation in a process that directly affects them, because you consider their intellectual capacity beneath you, that's just ableism tbh...
And this isn't even over direct participation! It's over putting an X in a box to decide who makes the decisions for you!
There's a VERY good reason why Youth Assemblies are such a big part of communal functioning in Rojava. Because their opinions and (more importantly) their consent matters