I agree that games that can be playable offline, should be playable offline. .
Destiny and Destiny 2 are my most played games of all time. Obviously, some portions of those games require online play - PVP, raids, strikes. But, probably 50% of the content could be played just fine, as-is, without getting online. Strikes could also easily be scaled to allow for single player, offline play. As we move further and further into the world of online play, I hope developers will keep in mind that many of us either cannot, or do not want to play online all the time, and that they will make content that allows us to play the way that we want to play whenever reasonably possible.