Aside from it just being a very good game (a new game in the all-time top 10 over at Metacritic is going to be news regardless), if you're hanging out in gaming enthusiast discussion a lot, there are a few other things going on that explain why it's generating so much buzz.

It came out at a lull in the release calendar. August isn't typically a hot month for gaming unless you're an NFL fan. It also ended up being a de facto console exclusive, so once the game started blowing up, the usual console war chatter spun up with it.

The other dimension--and one that surprised me--is it fed the "developers vs. gamers" spat to the point where it's been making headlines again. As you've said, one price for admission games have been coming out more, but I think there are some sour grapes around over Larian's successful graduation from AA by way of passion projects. I invite these developers to join in celebrating this release, as the success of games like these are bound to get more of the kind of game they'd rather work on greenlit.