For folks that like nature more than crowds, I recommend looking at Lindblad/National Geographic cruises.
They’re not cheap. I’ve gone on two, due to a connection with a staff member who received, as part of his compensation, tickets for an extra passenger. My cabin was belowdecks and right by the engine and with no window, but otherwise I had full run of the ship and all the activities.
The first one I went on was to Baja California in Mexico. The second was to Antarctica. Both were amazing, but the Antarctic trip was among the most incredible experiences of my life.
What sets them apart is the shore guides. Each day, except for during passage, there are 1-2 major expeditions. Some are in rafts, a few are self-guided with kayaks or what-not, but most are shore hikes. Often you have choices about where to go and how strenuous a hike you want. Whatever you choose, you’re accompanied by a naturalist, usually either a working scientist or a professor, who’ll lead the hike and tell you all about their areas of study.
So in Baja, I hiked with a Mexican botanist who showed us various cacti and described their role in the ecosystem. In Antarctica, a geologist showed us strange formations and described their history. In both locations, we learned about the human history of the area and how it intersected with the natural history.
During the evenings, after dinner, various scientists gave presentations. Wanna know more about cetaceans? About volcanic formations? About the aquatic ecosystems under ice floes? Go to the lectures!
It’s decidedly not everyone’s jam; but for me it was just delightful. If you can afford it and if it sounds at all appealing, I recommend looking into it as an alternative to party cruises.
(Closest it came to a party cruise was on the Mexican one, where on the last night I was hanging out in a common area, and a fitness influencer offered to flash the bartender if he’d make her a drink. “Please don’t,” he murmured, and poured her the drink.)