I have loved my cruises in Europe. I have taken six cruises (prior to Covid). Three were on Princess, two were on Disney and one was on
Royal Caribbean. I did the Baltics, British Isles, Iceland and three Mediterranean cruises (Spain and Italy, Greece, Turkey and Italy, Greece, Montenegro and Croatia).
Some things to consider when looking at cruises in Europe is to decide what your interest is in things like the temperature, history, city/towns, ruins, museums, entertainment, palaces, churches and nature, etc. These things might make the difference in which European itinerary might appeal to you the most.
I travel in the summer so my Mediterranean cruises were hot. I have also discovered that I can only visit so many churches and museums before I am bored. But I do enjoy visiting historical areas and seeing nature. So I always try to do a mix of tours. I also like to make sure I have downtime on the boat to break up a hectic schedule of touring so I look for a cruise itinerary that offers a few sea days.
My cruises departed out of Dover, Southampton (twice), Barcelona, Copenhagen and Venice. Venice was my favorite sailaway port.
These have been a few of my favorite cruise stops to visit: St. Petersburg (which I don't think the ships are stopping at now), Normandy, Ephesus, Iceland, Wales, Inverness, Edinburgh, and Malta. I preferred Mykonos to Santorini as Santorini was extremely crowded from the cruise ships the day we were there.
I hope you find this info to be useful in your planning.