As a theoretical construct this is valid but we aren't really talking about the game in its true form where you are playing with other human beings who you can discuss the interpretation of the rules and come up with a balance that makes sense. We are discussing a computer simulation of the game that is meant to be played in person. There is no "common participation" - rules such as alignment which are by nature arbitrary then get applied in a way which is arbitrary by whoever decides and we all just have to live with it even if it makes no sense.
Yes, the videogame version of 5E (even if BG3 followed it exactly, which it clearly doesn't) is a very different experience from tabletop with a DM. Alignment, plot, themes, and anything non-combat related are the great strengths of D&D, and are the reasons why it has been popular. They are what differentiate it from generic fantasy RPGs. They are generous and very useful for mature players that want to participate in a shared world, as a party. If you are very self-centered, the D&D party system is not going to work.
Those are also the same parts that are much harder to add into a self-contained videogame system, of course. I am not necessarily defending any published videogame adaptation of them, though. My comments are in response to a lack of understanding of those elements in core D&D, not specifically related to BG3. I think anyone who has deeper experience with D&D does not expect any videogame to be able to add them, for the reasons you mentioned. I did not expect any of the BG games to have them, and I still enjoyed playing them. I am going to enjoy BG3, too.
As for the problem of which aspects of Alignment to include in a videogame, and how to do that in a consistent way, I'm not offering a game design solution to that. I agree that it's hard to do, and I am willing to accept imperfection in a videogame version of D&D because of that.
Removing emphasis on Alignment in 5E was a mistake for a lot of reasons. It's too OT to start a debate about that. It was not done because too many players were whining about it in campaigns, though. These kind of changes are initiated at a very high level, due to political or cultural factors. So, yes, I do feel that the game would be better if Alignment were reformed instead of hidden, the way it's being treated now. D&D is very long-lasting, so hopefully it will return in the future after being improved. From a philosophical point of view, some of the conceptualizations of law and morality are a little primitive, but those definitions can easily be reworked without just abandoning the system.
Again though, that's kind of OT here. The fact is that any videogame is going to have to accept a reduced RP element due to the closed-system nature of a videogame, and the need for the developer to anticipate every possible decision a player makes in advance. As I said, I think most people with experience in tabletop have realistic expectations about a videogame being able to include all of that.
