So Cowboy Bebop is not a shonen. It’s a seinen Apparently it isn’t a seinen, but it would be if it started as manga. Trigun is a little odd because it shifted from shonen to seinen somewhere along its publication history.

I point that out because seinen/josei compared to shonen/shojo is more or less the equivalent of young adult fiction to children’s fiction.

Children’s fiction is supposed to be easy to understand. It should be filled with trope’s, kids can’t really empathize with things that are more complicated. Or maybe they’re at an age where they can but maybe shouldn’t, i.e. show with themes of suicide for an already teetering on depressed teenager.

All that to say that I think your family members perspective is… severely limited. Not watching Trigun because you’d rather rewatch Naruto is 100% their choice but… it’s a pretty stupid way to live your life.

“Pff, why would I watch these ninjas do magic? I can just watch space wizards do magic and fight with lightsabers. Naruto is trash, Star Wars is peak.” Or something.

Edit: I’m completely wrong about Bebop, it is not a seinen because it never started as a manga. Apparently that is an important distinction. I think if it had started as a manga, it would be a seinen.