Those specific users may be gone forever. But there are always more users, and there are always more markets. Don't worry too much about it. And I wouldn't worry about your visual design skills either. As you pointed out, the internet is littered with ugly but successful sites.
I do, however, recommend that you worry about that pesky "i didn't understand which problem you are solving" issue.
My advice would be to shut down your computer and talk to your friends and family. Go to dinner. Tag along with them in the grocery store. Even better... do something with them that you enjoy. And then listen to what's going on in their lives. What challenges are they facing? What challenges are you facing?
Start making a list of these things. You don't even have to write them down, but make mental notes of the things people struggle with. Every time you come across a challenge, think "could a computer help with this problem?" If the answer is yes, then think "how hard would it be to engineer?" If the answer is "not too hard for me to knock out a prototype in a week or two" then add this to another list in your head: promising ideas.
You'll need a lot of them. I have a list of about a hundred products that I think I could build in a week that solve a problem that I or someone I know cares about.
With that list, start thinking about the ideas in more detail. Think about some of the implementation details in your head. Maybe spend a few hours starting to implement some of the trickier parts of them to get a sense of how har they'd really be. Think about how you could make money off of them.
Notice which ideas keep popping into your head. Notice which ideas make you excited when you think about how they would feel to have built. Notice which ideas come up over and over.
You need to be doing this all the time.
Start telling people about your more promising ideas. Pitch to your friends, your family, your coworkers, strangers you meet at parties. Don't worry about people stealing your ideas. Any feedback you get at this stage is worth much more than the risk of losing an idea you have barely invested in. There's always another, better idea down the road.
Notice the difference between mild enthusiasm and genuine enthusiasm. "That sounds great!" doesn't mean much. "I need that! You should build that!" means a lot more. "I told my friend about your idea and they want it too!" means the most. If you find an idea that is already spreading before you've even built the site, that's a good sign.
Once you start to have ideas that a) solve a problem several people care about, b) are something you can implement, c) seem like they could make some money, d) excite and spread through your friends, and d) keep coming back into your head, that's when you should start implementing them more seriously. Write a 1-2 week minimum viable product.
I really think that if you do this kind of exploration process, you'll have a much stronger footing to stand on with your products. It's much faster to play with the idea in this way than it is to make a prototype, and you need to evaluate hundreds or thousands of ideas before you find a good one, so stick to this kind of fast evaluation process. Save prototyping for ideas that have already been vetted.