Good advice here, including that from Cyn above about doing some research on the potential impact of cruise ship crowds at your dream destination. That has become a regular part of my trip planning.
Personally, I try to altogether skip visiting places where there is a constant and heavy presence of large cruise ships (so increasingly, I'm going to places that are not overly famous and over-touristed), but that takes a lot of the world off your travel menu, so sometimes you just have to bite the bullet and try to work around them. In those cases when I do go where cruise ships loom large, I'll at least try to be smart about scheduling my time there - using the standard strategies like "get up super early and/or come home late, work hard to be out at the places I want to see long before the cruisers show up and after they've gone back to their ships." It can require some dedication (nobody I know is enthusiastic about waking up at oh-dark-thirty to go sightseeing when on vacation) but that's our world.
To the OP's question: another enthusiastic vote here for the Baltic countries - specifically Estonia, Latvia, Lithuania. They're lovely, uncrowded, not expensive, with all the traditional things tourists dream about (culture, castles, fortresses, palaces, scenery, history, great food, etc.), surprisingly delightful. There are some cruise ships and day-trippers in Tallinn and Riga, but they're not in huge numbers like at popular Mediterranean cruise ports, and both cities are plenty big enough to absorb them without feeling overwhelmed. Not much danger of heat stroke there in August, either.