There's millions of reasons WW2 was bad.

A comparatively minor but still very far-reaching one is that it framed all following political conversations be they real world or fictional in incredibly monolithic almost Arthurian terms.

It's absurd. Not bad narratively. But thoroughly absurd.

A solar system in conflict would be closer to Myanmar, the Balkans, Syria or the Philippines rather than Germany vs Everyone or various colonial independence kerfuffles.

A "realistic" solar war story would be less Inglorious Basterds and more Black Hawk Down or Shooter.

Not really good guys vs bad guys and more getting caught up in an absolute mess between other forces.

Not shooting space nazis in a heroic charge but running guns for the space Serbs because the space Albanians pissed your sponsor nation off. Also both sides probably have an axe to grind with the space Amish and caused their habs to fall into Jupiter when not observed but that's just an ugly reality you don't need to concern yourself with.

You got your orders.