Best way to get from cruise lline in Ravenna to vrbo in Venice?

If your cruise line is offering transport to VCE that will work

There are several ways to get from VCE to Venice proper-that info can be found here with a search
Water taxi will be your most expensive option-140 euros or so

But you might consider spending a night or 2 in Ravenna to see the mosaics and then travel by train to Venice-very easy

This thread has your transport options from VCE
https://community.ricksteves.com/travel-forum/italy/getting-to-venice-from-airport

If you are flying into/out of Rome FCO airport, you can take a train from/to Civitavecchia with a change at Roma Ostiense station.
But What has Ravenna to do with Rome and Venice?

To give you an idea about transfers from FCO to the cruise port. I remember seeing that the fixed rate taxi fee is around 130 euros. You can decide if based on the number of people in your party or what cruise line transfers may cost whether this is a good deal or not. As long as you go to the official taxi rank, it is certainly convenient.

Marco
Some cruises end at Ravenna-they claim that is “Venice”

Rome cabs is a good option Rome to cruise port. It is not a cab company but a car service. My sister used in June 2023 to transfer to cruise port. I used them Rome to airport without difficulty.
https://www.romecabs.com

Im not 100% clear exactly what you are asking. I think you are asking how to get from Rome (not the airport, I hope) to Civitavecchia cruise terminal, and from the Ravenna cruise port to Venice proper.
Rome to Civita can be done by hired car/driver, especially good if there are more than 1 couple and/or you have a lot of luggage. I've seen Rome Cabs (not a taxi) recommended often on this site and Cruise Critic. OR take a train/bus combo. On Trenitalia you can buy a ticket combining both. On the Trenitalia website use Rome (tutti le statione) and Civitavecchia porto. This gets you from Rome to Civitavecchia by train, then by bus to the cruise terminal. OR take cruise transfer.

Ravenna to Venice - easy by train. Take a taxi to the train station. Train to Venice Santa Lucia. Will require a change in Bologna or Fererra. In Venice take vaporetto to stop closest to accommodation. Or take cruise transfer.

If the cruise line offers transport to Marco Polo airport aka VCE, then I would take that. Then taxi or whatever to actual Venice. The post above gives VCE to Venice options.