I've read the pilot script for Defying Gravity and it's certainly not space opera. More like a conventional drama, ala Grey's Anatomy, with the backdrop of an intrasolar expedition.
That depends on your exact definition of Space Opera. At a basic level, any drama set mostly in space is a Space Opera. Everything else is a subgenre off of that.
True, the setting is mostly space but that alone doesn't qualify it as "Space Opera."
By definition, traditional Space Opera is an overly romanticized version of space travel with larger-than-life themes, melodrama, fantastic aliens and planets, vast empires, intergalactic war, and a grand scale.
Of course, we could say
Defying Gravity is New Space Opera as defined by the works of Iain M. Banks, Alastair Reynolds, and Stephan Baxter since it is focused on character development and verisimilitude. However, the scale is not grand enough from the pilot script, which reads very much, as the producers themselves have labeled it, a contemporary drama set within the confines of our solar system. I suppose that's where the
melodrama could come in.
You say that everything is a subgenre of Space Opera. Rather it is the opposite. Space Opera is considered a subgenre of speculative/science fiction.