The comparison is a bit skewed. The only reason that BG3 doesn't have any DLC is because the developer (Larian) said "We're done with D&D and WotC!", not because the IP owners (WotC/Hasbro) didn't want any DLC. Some people also forget that BG3 also had the Early Access scheme for almost three years... You know "Pay me for an incomplete and buggy game, and maybe we'll deliver what we promised in a couple of years...". Note: Have bought BG3, but not played it yet.
Something like Elden Ring did have DLC released this year, because both the developer and IP owner wanted a DLC. And looking at the sales of the expansion, also a LOT of customers wanted that DLC. DLC isn't inherently bad, it can be anything, from Horse Armour to a completely new campaign/adventure. In the case of Elden Ring it isn't a bad exploitative model. Note: Bought Elden Ring, not the DLC, have also not played it yet.
Touting BG3 as the be all and end all of computer games is just dishonest. It caters to a very specific niche. I even think that if Larian did the BG4 at the exact same quality, many people who bought BG3, won't BG4. Because at a certain point BG3 became a hype and thus a LOT of people outside of the niche bought into the hype, but aren't really the intended audience.
Something like Path of Exile is probably one of the best Diablo like games, it's a F2P game with a live service model. But it's again aimed at a certain niche. And something like Diablo 4 has people playing it that will never play PoE, while PoE is often considered the better game... There's always a relationship between intended audience, hype, etc. Sales != Quality.
That BG3 is a game you and many like, and that it sells well is something completely unrelated to actual 'quality'. I'm kind of interested how BG3 is reviewed in a couple of years when all the hype has died down.