Need to arrange transport Venice to Porto Corsini, Ravenna

Other than knowing the cost of taxi to cruise sip, that will the best way to go. In the total cost of your trip, flights, cruise etc, the transfer from train to ship is not a big cost item. Relax and enjoy your trip.

I'm not that keen on lugging luggage through the crowds in Venice, so I would suggest taking a vaporetto instead. Then the train to Ravenna. The port is about 13 km from the station according to Google maps, so the taxi fare shouldn't be that high; probably around €20-25.

Presumably the RC bus will take you to the boat, no?

Going back to the airport to take their bus, and not have to move your bags from one vehicle to another may be worth the bother to get back to the airport.

Depending on when your flight arrives and when the RC bus leaves( the next day), it may be feasible to get a hotel near the airport, go into Venice and visit for the day return to the hotel in the evening and then get the bus and minimize dragging your bags from place to place

The cost of the train from Venice Santa Lucia to Ravenna is as low as €16 per person, if one uses only Regional trains via Ferrara (about 3 hours in total). If you take a high speed Frecciarossa to Ferrara then a Regionale the time can go down to under 2h30m but the cost goes up to €34 in standard class (full “base” fare) per person.
www.trenitalia.com

The taxi from the Ravenna station to the cruise dock in Porto Corsini is a 13km drive, which, according to some Italian websites and blogs I checked, is a somewhat over €20.
So, overall, you are looking at about €55-60 for two people between train and taxi. If you take a vaporetto to the Santa Lucia station you need add €9.50 per person, unless you bought a vaporetto pass previously. There are 24h (for €21) and 48h (for €35) passes which might be a better option for your needs than the single ticket for €9.50 per ride (see below)
https://actv.avmspa.it/it/content/vaporetto

I'd pay the 120 € for a direct water taxi to the airport (it's 120 € per boat, not per person) and avoid all these transfers dragging suitcases for 90 miles.

Why cruise companies make people fly into Venice when they are sailing from Ravenna?

Why cruise companies make people fly into Venice when they are sailing
from Ravenna?

They don't make them fly anywhere. However they have to get there somehow, and there are only so many airports with direct international connections, and Venice is the closest. Bologna might be an alternative if flying from another European city; but I think the OP is coming from the US?.

I'd rather walk for 30 minutes or more between 2 gates in any European hub. The alternative is flying direct into the wrong Region, only to be forced to take two trains and a cab to finally arrive at the right port.

I think the OP is staying in Venice a day or two before taking the cruise, in which case it made sense to fly to Venice for them. But yes, Bologna airport is a better choice if one wants to go straight to Ravenna. There is only one train to take, and the Bologna Guglielmo Marconi airport (BLQ) has a people mover (Marconi Express) that connects the airport to the Bologna Centrale station.

Dani, if your Venice hotel reservation is refundable, I would cancel it and stay at one of the hotels near the Santa Lucia train station. This would greatly simplify the process. Then you can take the train to Ravenna and a taxi to the port. Or, you can take the Aliguna boat to the airport and cruise ship option for the $45. If you have more than one suitcase, I would do the option of heading back to the airport.

Be sure to take a vaporetto boat ride down to San Marco in Venice the day you arrive - after you’ve checked into your hotel, so you can experience a little of the beauty of Venice.

Thank you very much for all the helpful information!