What you've written addresses quite a number of issues, some of which apply to beaches in general.
Clothing optional, well, I'd say that every sim in OpenSim that allows nudity is clothing-optional except for Amoa which has a technical barrier against clothes. Lots of people don't know about "dress codes" on nude/clothing-optional sims, and many of those who do don't care. So a nudity requirement won't drive away that many people.
In fact, you can have 20 people on a sim that says both on in-world signs and on OSW that nudity is required, and you'll still be the only nude amongst women in clubwear and men in black leather jackets and jeans. Maybe there'll even be people who complain about your nudity or even demand you put some clothes on.
As for decoration, that's really something that's often neglected. The possibility to walk into the water or even swim fits here, too. It kind of reminds me of two threads about beaches I've started a while ago, especially the first one (
https://opensimworld.com/post/85841, https://opensimworld.com/post/85884).
There are so many issues with how beaches are built. Ground dropping from 21m to 0m, and that's supposed to be the water line. The whole beach being a mesh shelf with nothing under it but water, and when you want to step into the water, you fall down 20m. Beach decoration only consisting of a few palms. Or a few palms plus sex furniture, but still nothing else.
Beaches are either just simply there and need to be decorated or too obvious porn sets. Nude beaches are often nothing more than decoration for nude party/sex sims.
Granted, I guess most beaches were built by people who have never been on a real beach in their lives, be it tropical or otherwise. They don't know what a real beach looks like. And how are they supposed to know how to make a beach immersive if they don't know what being on a beach feels like?
Activities fall under this, too, and be it just a bit of mild role-playing (not hardcore RP level Fitheach Eun, but "playing it real") being possible. I mean, it doesn't have to be a second Coney Island (
https://opensimworld.com/hop/87886). But most beaches only offer you one or both of these two activities: lie in the sun, have sex. Okay, three, Greedy.
This takes me back to swimming again. Now, this would be one obvious activity to offer on beaches. Make the seafloor slope down as gently as it would in real life, and add a swim rezzer or a few so that people don't have to run around half your island to swim. Surfing would be the next step, and it has been done a gajillion dozen times, so there are enough people whom one could ask how it's done.
Dear sim builders, just because you don't care for this, and you'd never make use of any of it, doesn't mean nobody does and would. Also, whatever you drop down on your sim, test it. Broken items should never be excused with "at least you've got something to look at".
Lastly, as you've written, it's one thing if sims have their issues that can be fixed. It's something else if you ask sim owners to fix them, and nothing happens, even if it's obvious bugs.
Some are just busy elsewhere, be it in real life, be it with another virtual project. Some haven't read your message because they haven't logged in in months or years.
Then there are those who don't fix bugs because they say it works for them (sure it does, they're privileged sim owners and not Hypergridders like the majority of us, and they've got their personal landmarks that we don't have). Others can't take any criticism, and bug reports fall under criticism for them. Others yet again say they have a personal vision of their sim, and what you see as inconvenient or even deal-breaking is part of this vision for them. And then there are those who simply can't be bothered.
By the way, I'd like to add one point which, I think, would contribute to the popularity: The sim should be at least halfway up-to-date. This refers not only to the underlying OpenSim version, but also to the decoration. Nothing against prims if they've been put to good use. But we've got something better than beach towels with exactly one built-in animation. Pairs of poseballs for dancing are just plain outdated and have been ever since Áine Caoimhe has made the Clubmaster. And I wouldn't count on vehicles scripted for TSim or older to still work properly nowadays.