However, the game IS being marketed toward "niche" or very specific audience: it is a "main entry Baldur's Gate game" and a "D&D 5e game". They were pretty clear in marketing it as such, and therefore, in my opinion, it is fair to hold the game to being appealing not just to any RPG player, but specifically to these groups. And yes, Larian have made it quite difficult for themselves...
The thing about BG1&2 is... you don't need to understand the systems to enjoy the games. I don't consider myself a hardcore player. To this day my understanding of all the 2AD&D systems is... incomplete at best. Yet it never stopped me from enjoying the games, and not because I had nothing else to play.
Exactly right. Larian wants to ride the wave of rising popularity and WotC wants inspire more devs to make video games. For many, this will be their introduction to the ruleset. As @Ellenhard said -- BG2 encouraged more people to take an interest in the PnP version of the game. Let's hope this game has the same impact.