But they're two completely different experiences that are entirely independent of one another. You can enjoy the campaign without any influence from Online, and you can enjoy hundreds of hours online without ever having to touch the campaign.
I greatly appreciate that there is 0 influence from the Online game in the single player campaign. I'm in full agreement with you there.
Besides not getting single player DLC because Rockstar wanted something more profitable, what don't you like about Online? The only real complaint I have is that there isn't a "mute all" option in the player menu.
Honestly, I don't like multiplayer games in general, and I stopped playing online games years ago (I only played MMORPGs, and the occasional Team Fortress 2). But I tried playing, and it's just super cumbersome to me, I don't like anything about the design, it feels almost like an MMO but not quite up to that. It also heavily persuades people to play in groups and I just don't like that because it gates off content for people who just want to do stuff alone but want to participate in a 'living' world with other humans playing alongside them. The other is, of course, Rockstar ignoring the single player game to chase the money in the online world (two words: shark cards...).
Also, they did promise single player DLC which I was so hyped about, then they just quietly pushed it away, and then denied ever saying it was coming, so I'm still salty about that.