I have sailed solo on Carnival, Norwegian, and Royal Caribbean. All on the west coast though, but 3, 5, and 7 nights.
I don’t generally go to the single/solo meet ups because I like my own company best (neurodivergent and very awkward with new people) but I did once on the Norwegian sailing because I was staying in a studio and had access to the solo lounge. I’m 33, I was easily the youngest person there by a couple of decades. Did meet some nice women at a painting class though and we ran into each other a few more times throughout the sailing, even ended up on the same excursion.
I also have future solo sailings planned on Celebrity, Holland America, and Princess.
A cruise could be less relaxing than an all-inclusive. On a cruise, there’s a lot of action, people, and activities—not much peace and quiet, especially on the shorter itineraries that are usually a little wilder.
There are many families on cruises, and the majority of passengers are seniors, unless you’re on one of the few upscale cruises reserved for adults. would make it unlikely for you to meet unmarried women while on the ship.