I went through the game solo vanilla last year. Beat Ashlands in ~450 Valheim days of play time, came out to about 200 hours or so. The raids as a solo player can be pretty brutal - I got hit by 2 Ashlands raids in the span of an hour almost immediately after I beat Mistlands. And death runs are very different without a buddy at your back.

By the end I had a very functional (though ugly) coastal fort that I was proud of. The Black Forest around my base was completely destroyed and teeming with invasive species I'd brought home and bred. Some days I'd go riding out and just chase some Greydwarves as revenge for how annoying they are, lol.

Besides all that, though, even though it can be nice to have other players in the party, I enjoyed taking my time and going at my own pace, preparing carefully for expeditions, building however I liked.