You've forgotten the actual reason games win GOTY. It has surprisingly little to do with how "good" the games are, or how much money was spent on them, they don't have to have high-end graphics (Untitled Goose Game, 2019), or incredible writing (Fornite, 2018), or even be bug free (Skyrim, 2011). For a game to win a GOTY it has to be influential. This is not always the easiest thing to quantify, because it relies on analysis of the goddamn zeitgeist, which is getting harder to do each year with how quickly trends roll over. But even then, what I said before still holds, different companies judge how influential games are differently, and it's rare for one game to top everyone's lists.
To put it simply, BG3 will probably win a GOTY award, because it's been one of the most influential games of this year, it has sparked many conversations about and within the industry by powerful and knowledgeable people, conversations about early access games, about the growing reliance of the industry on post-release income generation which continues to upset consumers, and about sex and sexual content in video games. Knowledge of the game reached beyond the normal video game sphere of influence, so that people not even associated with video games were talking about the game (thanks, bear sex). It's only one of a bunch of games that have all released this year and received high critical acclaim (according to metacritic), but it's easily one of the most well-known.
