I just came from there a few months ago. No masks anywhere!
The upper keys are a bit suburbia. They are very strip mally and groomed. THe middle keys are better i think. Marathon was nice just to get away.
The keys aren't really known for beaches. There's a few but it's not like Hawaii where there are beaches everwhere. A lot more rocky and swampy. The sunset are actually not that great since the islands span East West and most of the views are North South, so you have to dig around for a good spot.
Key West is expensive and loud. Stay somewhere else and go there for a day trip. It doesn't do anything that Miami Beach doesn't do ten times better. Oh but the Hemingway House is pretty neat. They have 57 cats on the property sleeping around in his bed and on his writing nook.
For military go to Boca Chica key and drive to Geiger beach. You can see the fighter planes taking off from there. (Warning, it's not a pretty beach so don't bring towels and umbrellas. More like a hiking beach.)
Also check out the Key West Botanical Gardens. They have boat wrecks from the Murial Harbor trip. Pretty amazing to see what these folks made float and move from Cuba. This is actually on Stock Island next to Key West.
Best restaurant I found was The Marathon Fish Market. They will cook you what they caught that day. Funny but a lot of the fish in the Keys restaurants is frozen and shipped in. They actually don't catch enough dolphin fish to meet demand so you can expect to eat the same fish you get in Cedar Rapids. I was kind of surprised how much the fish tacos sucked at all the tiki bars and then a local told me this.
You mentioned that you aren't into ocean activities. Try The Marthon Lady
https://marathonlady.net/If you don't know how to fish, they will do everything for you including baiting your hook and unhooking your catch after you reel it in. If you aren't partial to fishing, this might be fun. You are also on a boat with 50 other people equally as clueless and the staff takes care of everyone. Great experience for a noob. And a lot of restaurants will cook your catch for you.
Best part of the keys is the drive. It really is the coolest drive there is. Just exploring around the nooks and crannies of the middle keys is a lot of fun.