This is my thought. Not a bad idea to book through Costco. You will get the package you buy. And nothing wrong with that.
But if you go through a very reputable travel agent. You will get the vacation you want.
If you go to Italy. What is really your goal there? See if their food is as good as In N Out? (yeah, I had to throw that in there) Sight see. Go to a hole in the wall place? etc etc.
Here is a for instance. A friend of mine went to Italy. Guess they researched it a bit. And they went to the Vatican. They reserved like 6 months or so in advance for a special tour that would take you through the Catacombs of the Vatican. Only so many people get to go a day, in other words, it's very limited. But from the initial friend, and a friend I recommended it to afterwards. They said it was well worth it.
So make the most out of your trip.