I don't think you have pinpointed where BG3 value really is. It clearly isn't in its simplicity since Larian have made simple CRPG with moderate success for a while now. I am pretty sure that BG3 would have been as popular if they used the Divinity rule set. In the past years, if you wanted to play a RPG, you had to choose between a game with good production value but shallow depth or the contrary. The true game changing argument this game has is that it simply has both.
Also the WoW argument doesn't apply for a single player game. MMO games are meant to be relevant for the longest amount of time. What companies who tried to make a WoW killer failed to realize is that players were already deeply invested into it. Why take the risk to play a clone when you have already spent years into your character? Sinking cost fallacy is a hell of a drug.
