To me it sounds like proponents of not having decent CSG tools never made games single handily, especially featuring actual levels and not terrain or grid based modular pieces.
It’s fine when a team has several artists who can churn out modular pieces or even make actual levels. However, where there is one artist that is also a level designer, or dedicated level designer who comes from idTech/Source, proper CSG is invaluable.
It shouldn’t be an argument whether to have it or not. It’s already there, in the engine. Just needs optimization and tools on par with Radiant/Hammer or better yet, like Trenchbroom: TrenchBroom