... with 600ms latency. Starlink will blow them out of the water.

Oh, sure, the latency will be lower - it's just that without these satellites it was simply not possible to get continuous coverage on long over ocean flights, so something is better than nothing.

While for airplanes I think the latency might not be that problematic (I think VoIP in plane package full of people would not be very welcome) you indeed want low latency connection on a cruise ship.

Regular web browsing also benefits massively from lower latency, not just VoIP.