I'm wondering if you think that low water affects only certain cruiselines! If the water level is too low for a ship to sail, no ships sail. Mother Nature does not play favorites!
Perhaps instead of choosing another cruiseline, you should choose another itinerary. I haven't heard of any water level problems on the Rhone or the Seine (river cruises in France), or on the Volga (river cruises in Russia). These are fabulous choices!