Unbias doesn't explain the 80% metacritic score from professional reviewers.
I'll explain it easily.
When they reviewed the game it was at release.
The reviewer only played the game for a short time compared to many players and thus didn't hit many of the issues people have when they play it a lot.
Even then many reviewers had a caveat about lack of content and things to do, many of the reviewers expected this to change in post release content, We now know this hasn't changed sufficiently enough in the 1 and a bit years since release.