The key thing that makes me lean more toward this answer is the fact that Baldur's Gate 3 can be played in Multi-Player mode.
(In fact, there is a case to be made for the description of BG3 as a game that "you can also play Single-Player, although really, Larian is designing under the assumption that there will be 2-4 human players, each controlling a single character, and that this is how they are doing 100% of their internal testing". But that's another story. At any rate, BG3 is clearly advertised as Multi-Player. It's not something that you can merely "also do".)
It's common advice for tabletop groups that all of the players, or none of the players, should have an optimised characters. And that's something that should be discussed during session 0.
You don't want a mix, because DnD is a cooperative game, and everyone should get to have their moment where they shine and make a difference. If one player has an optimised character and constantly outperforms the rest of the group, it's probably less fun for said rest of the group.
If a player plays BG3 with their partner, they can probably do the session 0 discussion. I mean, this applies to any close, regular, tightly-knight group of players. But in a more casual group of 3-4 friends, who are all video gamers but with one who is also BG3 expert/rules-savvy, and the group isn't aware of the tabletop/coop game common wisdom about optimisation and relative balance, there is easy potential for mismatch to happen.
I'm not saying OP builds should not exist. It's fine, to some reasonable extent. And in DnD 5E, there is room for somewhat OP combos. But I think that Larian's ruleset only exacerbates the difference of impact between an OP built character and a more normal one (i.e. the difference between floor and ceiling is greater in BG3 than in 5E).
This is such a critical point that lays bare a lot of the issues I have with the current game as a Baldur's Gate sequel. I mean I can understand why it would be so, and especially why the Wizards would want it that way, but I do feel like it ignores a particular sort of D&D player who's entry point into D&D is not the MP TT session, but rather the SP CRPG 'session.' It's not that there isn't overlap or can't be overlap here, but these are such different avenues into the basic D&D experience (and with rather different end goals in mind for what a really solid playthrough should feel like or what can be accomplished in general terms) that it's really hard to satisfy both with the same game/setup. For a very long time, there was an invisible wall separating the SP CRPG campaign experience from the more authentic Co-Op type TT experience on a computer, where the latter was sort of impossible to achieve and the ultimate of the former was essentially the old gold boxes/BG1. Now the situation is sort of reversed I guess, and some of that old SP CRPG territory has been ceded to games like Pillars or Pathfinder, where the more official D&D computer games are seeking what is essentially a digital emulator of the TT experience (so Solasta, BG3, what they're trying to do with Beyond/One etc).
D&D has always been in an oddball position, because you basically need 3 or more players for the TT game to actually be fun - a Dungeon master + 2 or more PCs. Sure you can do a DM +1, but that's a lot of commitment/pressure on both the DM and the PC, and it just doesn't work nearly as well as a DM+2 or more. There are a ton of classic board games that are like this, Risk and Monopoly spring immediately to mind, as relatively simple boardgames which are pretty rough/boring if you only have 2 players, but potentially a lot of fun if you have 3 or more. And of course there are virtually no classic board games that are designed as a purely SP thing, since that's just rarely the point of a board game. But D&D is not just a boardgame or a TT game.
Because of the long shadow of CRPGs and just the general fascination with Dungeons & Dragons as a kind of cultural or artistic fantasy phenomenon, it also has really strong appeal to people who we might generously describe as the D&D loners. I mean here kids who grew up with it a bit more like I did. For me, a lot of times when I play a game like this or evaluate it critically, I try to recall what it was like for me when I first came into D&D. Sure I know too much about it now to fully recapture that first impression vibe, but like the skeleton in the Last Unicorn "I can remember" and so I try to do that lol. I didn't have siblings or cousins my age or a consistent playgroup, but I still loved D&D all the same. I bought the sourcebooks for the art and for the lore and story material contained in those tomes, collected miniatures and all the rest, but my actual in was the CRPG. The authenticity of that as a true D&D experience might have been debatable, but it was nevertheless a very strong intro and threw the Gate wide open to bring me in, and perhaps many more people than might otherwise have been possible if there is no such thing as SP D&D, if that makes sense hehe.
Something like a Circlet of Fire, which would probably have been great fun as an SP experience type cookie for me, becomes a bit of an OP game breaker when the goal is a balanced MP Co-op experience. Having the MC totally outshine all their 'companions' probably doesn't matter much to the SP experience, but it definitely does when it's a group play dynamic. I just think it's a different beast, such that you'd almost wish for two version of the base Campaign, or two types of launch settings- one designed explicitly for a single player to make that as engaging as possible, and another for MP/Co-Op. Some of the things which might make for a more fluid Co-Op campaign and control scheme, actually work against the SP campaign, and vice versa. In this case it's the loot at issue, but even down to stuff like how many "companions" the game is meant to accommodate, it is ever present. So for example, I think a party of 4 is probably pretty ideal if MP is the jam, but not so much for the Godmode full party control game which was the hallmark of CRPG and BG1/2. It's a real bind for the Devs I'd have to imagine, and doubtless the source of much grumbling, depending on what your preferences are or expectations are for a BG3.
