I can tell that you do not know what you're talking about in relation to Destiny. It's cool, I'll break it down for you.Halo and other FPS like COD have dedicated traditional campaigns in which you play levels and events, and even use weapons that you can't use or experience in multiplayer. They are fully separate experiences.
The campaign in destiny whether you are playing alone (which you can't really do cause you have to be online) or with a group is the same as the non-campaign stuff. No dedicated levels, areas, or experiences.
If you are always online, you are not playing by yourself
-There are weapons/relics are PVE exclusive in Destiny like any other game.
-PVE and PVP are fully separate experiences in Destiny
-The game being always online doesn't mean you cannot play it by yourself
You're wrong on so many levels. Titanfall and Destiny do not share much of anything in common, outside of the fact that they are both online only games. I'd say 80 to 90% of Destiny's PVE can be played by yourself. And 100% of the Story Missions can be played by yourself. You're reaching and I don't even understand why.