I think that the portable generators used on deck are a problem, but I don't often hear anything from gensets installed below.
On my boat, I have a genset in the engine room, which is dead center in the boat under the cockpit (center cockpit boat). Its loud below decks, but not from outside unless you get near the exhaust and hear the splash.
We generally only run it to charge and when it would be convenient to have AC power for some reason. The inverter does OK for most of those.
On our trip to the Bahamas, we found that an hour in the morning and and hour in the afternoon took care of the charging. We generally did this when we were cooking. This allowed us to freely use the microwave/convection oven and to run the Air Conditioning if the heat was building up in the cabin from cooking.
I wouldn't go cruising without one, but I am not a purist. I do like my quiet anchorages and try to respect that others may feel the same.