But if you have never been to Crete, and if you think you really want to see Knossos (as against just ticking the box that says you've been there, done that) that's what you ought to do.
Some people are disappointed in Knossos, and the restorations are a bit naff, but on the whole it is a fascinating site, and if you really look around at all of it, not just the "palace" and the "throne room" but take your time to wander around the whole of the ancient city, you'll see places where people lived and worked, and it has a powerful atmosphere if you let your imagination work. The pottery workshops are especially touching, I think.
The best time to experience Knossos is in the early morning, before the crowds arrive and before the heat of the day sets in. If your cruise ship docks early, and you can organise a tour to get you on your way quickly, you could have a memorable experience.
Seeing Knossos is greatly enhanced by (a) reading about it before you go and (b) visiting the archaeological museum in Heraklion. The main museum is still closed for renovation, but the exhibition of selected artifacts nearby shows all the major pieces, and is excellent.
Have a nice day whatever you decide to do.