Visit to Plitvice Lakes?

For me that is a dependent upon your schedule, what else you have planned and what you will miss if you spend time on Plitvice. For me on a scale of 1 to 10 it was a solid 5 because of the extreme touristic nature of the whole thing. Beautiful if you can be there alone, but that probably isnt going to happen. BUT, if you have the time and it isnt taking needed time from better things .... sure, why not.

EDIT. Okay, I will be fair, was a solid 7 out of 10.

This is really an open-ended question now. Where do you stop and how long do you have? Or are you staying extra days AFTER a cruise?

I love Croatia but I am not sure about “must-sees”. Surely you spend time in Dubrovnik. I really enjoyed Plitvice, but in all fairness I went in 2021 when it wasn’t crowded. Some of my best memories are simply of wandering streets in different cities.

Well perhaps I should have asked -What are the Must sees?

That depends on where you cruise is stopping, stopping for how long, and the time of year.

I've been to Plitvice Lakes National Park three times. The first two visits (decades ago) were great. My 2015 visit was extremely disappointing because it was a day trip from Zagreb and the travel world now knows about Croatia. The park gets totally swamped with day-trippers, so you really must spend a night in or very near the park so you can see it either late on the afternoon you arrive or early the next morning (or both). It's a beautiful place, but seeing it as part of a plodding mob of people practically walking on each other's heels is not a good experience.

I would go, spend 5 nice hours.
Should take the short boat trip on the lake
A good 7 out of 10
At least a 7 on my list.

We were there in September on a Rick Steves tour. We all started out early to beat the crowds for the first couple hours, but I didn't find that section all that spectacular. The second half was pretty much continuous lines of people in both directions. The Great Waterfall at the very end of our hike looked to be the best part, but the walk over to it was so crowded that our guide had us skip getting close to it. We did see it from the trail going up, but I have to say I found just about everything else we did on that trip more memorable.

Plitvice Lakes NP is beautiful and unique and one of our favorite places. The best way to see Plitvice, IMO, is to spend a night there. Arrive at the park in the late afternoon; visit the Upper Lakes; start your hike around 3 or 4PM. Then visit the Lower Lakes the next morning, starting your hike between 8AM - 9AM. You will be done by noon. And you will avoid the worst of the crowds. That is what we did in September 2019, and it worked out very well for us.