Yes, we could make a larger cabin with the same weight constraints using modern composite materials.

But even with lighter materials, you would still not be able to accommodate more passengers comfortably. The majority of weight-per-passenger will come from water (which every passenger needs for showering, toilets, food preparation). You would need to land regularly just for passenger hygene reasons. So I still don't expect blimps will be a 'comfortable' alternative to cruise ships.

Random fun fact: The Hindenburg had a grand piano made from aluminium, as a regular piano would have been too heavy.

Cruise ships are absolutely massive. They're floating cities, housing and feeding thousands of people. The new materials would have to be very light indeed to scale from 50 to 5000 passengers.