Balance is a valid concern. Calling a point of view moronic or selfish because it doesn't line up with your's is unhelpful and hypocritical.
So with 6 people, you'd have 50% more firepower. So now to balance that you'd need 50% more or stronger enemies. Which would negate any time saving. At best, fights would last just as long
Now with 6 you also have 2 more people you have to gear up and manage their build and relationship. That can add a lot to play time in a game that already has a slow pace.
Playing DOS2, Lone Wolf games went noticebly quicker than 4 player ones.
DOS2 also had more freedom with its rules and could balance out lone wolf with double stats and more AP
Now with BG3 they're more restricted where the more they stray from dnd rules, the more upset people could be. That's where balancing can get complicated. So add more ideas to help with that, rather than leaving it up to the devs or throwing insults.
Maybe less EXP for bigger parties and more for smaller ones