Solo and multi can be quite different experiances, both work thou. There is lots of experiances to share with others, but mechanically there is nothing really that makes solo unviable. And solo you can play your own pace instead of waiting for / being drag about by others.

There is not too much grind solo, except if you want to build a huge base for the fun of it. But then there are console commands and other tricks to make it easier if thats your objective. The game really have many ways to enjoy it, thats why the answers you get are mixed.

If you are looking for a exploration and building game, it might be a bit "hard". But the combat itself leaves plenty room for skill or gear to shine through.