You could probably make this case for Star Trek: The Next Generation, Deep Space Nine, and Enterprise as well. TNG and Voyager probably fall closer into the "highly-episodic" category, while DS9 and Enterprise tend to be structured around larger ongoing plot lines. I think they all have the same kind of merit as Voyager with regards to discussions about issues and moral decisions.

Depending on the 11-year-old, you might be able to make a case for Seth Macfarlane's The Orville, which can be a bit more hit-and-miss, but does have some truly excellent episodes, particularly in Season 3.

The newer Star Trek series coming out are probably too gritty if the parent is worried about age-appropriateness (I believe Picard has a TV-MA rating?) and unless you really like The Original Series, it's pretty noticeably a product of its age and I personally had trouble staying engaged by it when I was that age.