If a significant portion of players have to use a mod, the same mod, to achieve a higher level of satisfaction from the game = bad game design.
For DOS2 players, you will remember in the Definitive Edition that Larian ended up officially adding some of the things from popular mods to the purchased copy of the game. No one wants to wait over a year or more after BG3 release for them to realize and add these features to the game.
Some people care about Steam achievements. If you have mods, you cannot get achievements. Mods are also unstable after updates and may require constant updating after every patch and every hotfix. It could also be cumbersome for some to initially install.
It is the easy way out for someone like Swen to flat-out say that they will rely on mod support for certain issues, i.e. things that people do not like.
