"Save to Web" Files Not Usable

Image maps were used during a time, literally 20 years ago, when everyone assumed web pages would be seen on big desktop computer screens. An image map requires HTML code that locks the images to a specific positions and dimensions; the image map won’t work without that code. But that old code does not work with today’s dynamic, responsive layouts that can adapt to desktop and mobile displays of different sizes, shapes, and resolutions.

Of course, that history is not something many newer users know about, so it’s understandable that someone might learn about image maps today and not know that it’s already years out of favor as a practice. So that’s not your fault.

The reason an image map doesn’t work with Facebook and other social media sites is that they let you upload only the picture, not any custom layout code that you might to keep with it. This is partly for security reasons; sites can’t check all the code that might come through in case it has malware that would infect the network. So Facebook, Instagram, YouTube etc. only let in the picture or video, because that’s safe. The only clickable features they allow are the ones you can add within their respective services and apps, like the call-to-action buttons, end screens, and cards you can add to a YouTube video.

You might get away with posting an image map on web pages you control, such as on a self-hosted WordPress site by inserting the image map code into a Custom HTML block. But even if you do that, the old-style image map code might completely break down within today’s responsive layouts driven by CSS and JavaScript, especially on mobile devices which are now at least half of all web traffic. I’m not even sure how well web browsers support image maps any more. So even if you could implement image maps, they might not be effective where you most need them to be effective.

I think (but am not sure that) a way to make clickable image areas that follows today’s web standards might be to overlay interactive CSS layers over a single image. But even that only works on web pages you control so you can add any code you want; no social media site will allow that.

You have to learn how each platform works. In this case it's not Photoshop that's doing something wrong... each platform you're talking about (Facebook, WordPress) etc. works differently.

Facebook does not have any feature where you can tap part of an image to go to one website and tap another to go somewhere else. It's just not have Facebook posts work.

WordPress makes webpages with can do a lot more than a simple Facebook post. There may be WordPress plugins that let you create what are called image maps, which create multiple clickable areas within an image. But normally that's not how I'd think about a WordPress page. There would be multiple photos, buttons, etc each with different links, not just one image with many links inside it. These days it's rare that I ever see image maps being used anymore. I can't remember the last time I saw one. Things are just designed differently.

In summary, you'll have to learn how to fully and properly utilize each platform. Photoshop will come in handy when creating photos and graphics for each platform. I know there's a lot to learn, but I hope this helps and best wishes!

"I now find that the resultant files are worthless... What am I missing?"

Results are not worthless just can not serve for what you have in your mind. You need to learn more about topic and how things work.