The reason I don't see The Orville becoming a cultural phenomenon is because it is basically TNG.
Yeah, and TNG spoke to a lot of people, did it not? I don't think Orville needs to reinvent the wheel. Quite the contrary. In the world of modern tv they are already kinda special and "new" by being old school and by depicting an - at it's core - optimistic and fun look at the future. I cannot speak for anyone else, of course, but while I enjoy shows like nBSG, I'm more than just a bit tired of all that bleekness and darkness. Especially in science fiction. When I watched TNG it always made me longe for that future and it made me want to build it because I wanted to live there. When I watch stuff like Stargate Universe, or Discovery or Expanse, all I can think is "thank god, I will be long dead by then". ;D In a time of constant stress and burnout, Orville is great escapism without being shallow.
Okay, becoming a cultural phenomenon like TNG is wishfull thinking, but... I think the potential viewership is there. Like I said, I could see it go either way.