23mm is a lots slower, I’d wager a good 40mm actually be better than the horrifically small 23mm that a lots of tyres manufacturers nowadays no longer make.
There is a compromise. You're only considering rolling resistance. 42mm tyres are significantly less aero than 23mm and this will be a not insignificant drag at higher speeds.
And if one's using aero rims, there's none optimized for such fat tyres.
23mm is a lots slower, I’d wager a good 40mm actually be better than the horrifically small 23mm that a lots of tyres manufacturers nowadays no longer make.