It's a bit of a roulette wheel. If you think you have to claim the full amount on all cruises, yes, it's insufficient. But if you think that if you have to cancel a cruise within the penalty period, then unless the trips are very close together, you have time to cancel the others with minimum penalty. That's the risk factor involved.
And usually, unless you are a big time spender, between the maximum Allianz allowance and credit card coverage (depending on which credit card) any single trip can be mostly covered if not fully covered.
On the other hand with cruise prices rising, the rule may become nearly covered.
But to us, the real important part is the medical/evacuation/repatriation coverage, and for Allianz, the maximum coverage is per trip, not per year.