Yes. It's fairly worth it. You can trade with other players, buy and sell turnips at their islands, use the Dream Suite, get furniture variants that aren't native to your island (specially since Redd doesn't sell everything). Lots of stuff. So far we don't know of a way to get the other non-native fruit, either, so you'd be stuck with your native, the 'sister' (the non-native fruit the game assigns to always appear for you on Miles islands), and if you're lucky a third via your Mom at the start. There's no way to get all 5 fruit types without online atm.
For Pocket Camp or the linking? Both things are free.
