I have the same generator in the same RV. The exhaust routing is dumb. On the LP version they route it out the back which is a common mod for those with diesel generators.
Regarding the noise, you cannot compare it with larger diesel generators that are water cooled. The water jacket makes a great sound insulator. I have a 24 HP Yanmar excavator that's almost as quiet but it's water cooled. Another issue with the Winnebago is the vibration from the generator excites the structure of the RV which seems to make everything louder. This one I peg on Winnebago but they make no claims about how quiet their generator installation is so buyer beware. One thing I have noticed is just letting the bin door in front of the generator hang loose makes it a bit quieter. I may put some sound insulation on the back side of it and fill it with foam so address that.
My main solution is to use a portable Honda for battery charging. I will be adding solar is I dislike generators in general.
There is another thing I know of that two people have done. The replaced the OE generators with permanently mounted portables. One is a Honda 3000 and the other is a Yamaha 2400. The guy with the Honda has a 12 gallon fuel tank for it so it will run a long time. He says it's super quiet and of course weighs less that the LP unit he replaced. If it's any consolation the LP unit isn't terribly quiet either I'm told.