There might be no “requirement” to speak, but the culture of River Cruises is that you make new acquaintances and have a polite conversation if you are sharing a table. Socializing is part of the experience.
If having a table for two is a “requirement” then River Cruising probably is not for you.
We always have the pleasure of meeting new and interesting people on our cruises. The pre dinner cocktail hour is a big part of River Cruises also. It is almost impossible to sit by yourself. If your wife can’t hear others I’m not sure she’ll be able to hear you either.