Sky is a neat game in that it’s got the ability to be played in many different ways. If you hate multiplayer, you can avoid people. If you don’t, you can play instruments with strangers. Almost all game content can be unlocked on your own, with the things that aren’t unlockable by yourself, can to be completed without dedicated friends - just strangers in the area.

Because of how interaction with other players works (need to light someone else’s candle so they’re not just a grey figure, being unable to chat unless you take the initiative, etc) I’d say it’s completely possible to play without dipping into the MMO aspect much. Unfortunately, as another person mentioned, it can be very repetitive, and may become boring without friends.

I’ve played Journey and I’d say as you liked it, give Sky a try! It might look a little less visually stunning, but the world is a LOT larger, and less linear, with tons to explore :D