We have been on many cruises in the Caribbean and Western Mexico, but this was our first European cruise. I had been to three of the destination cities more than 40 years earlier, as a teenager, and my husband had never been to Europe.
It needs to be said that you are at best "sampling" the cities, as virtually every port deserved more time than the 8-12 hours we had in port. If your primary interest is Italy, don't do it by cruise ship. Both Florence and Rome are 1 1/2 hour train rides, each way, from the port.
Within those limitations, this was an incredible cruise. The ship was excellent. They had had a novo virus outbreak the trip before ours, so they did an extra thorough cleaning of the ship, and the hand sanitizer brigade was waiting for us every time we re-boarded or walked into a dining room. Food was excellent, and attempted to mirror some of the local cuisine. The ability to do "anytime" dining was a great plus (only available if you pre-pay gratuities).
We came into Barcelona a day early, and quickly wished we had at least one more day. If you are going, get tickets ahead of time to see the Sagrada Familia. We had a hotel in the Gothic Quarter and could walk to most things in the Quarter. The Barcelona subway got us to Sagrada Familia, and was very easy to navigate. If we had more time, we would have explored more of the city by subway.