The main thing you've gained is sharpening a lot of skills. You can run your own software business if you want to. You're learning the hard way. Life is a good teacher with reflection, albeit unpleasant sometimes.
Validate even MORE about the problem, AND the solution, before building out the solution in a substantial way, or at all. Is the problem clear to the people who have it, and one of their top priorities? Find out by communicating with them, ideally in person, but video chat works and written forms if that's all that is possible. If a competitor exists, great! What's the value proposition of your similar product/service? Why is it so good someone who uses another should switch, or what makes it compelling for someone who is evaluating your product/service?
Instead of positive interest, how many people will sign up in a form you link them to, or a landing page? How many will give their email or some contact information so that you contact them when your thing launches? How many say "I have $x and I will pay you that right now if you make this problem go away!"? How many people will read your blog post about how frustrating a certain problem is? Saying "Yeah, I hate that problem", but not being willing to do anything else. That might a dead end.
Another strategy is to build something that solves your own problem. Minimally, it will be useful to you. If it's useful to you, you won't be putting "effort into something nobody wants". If you have the problem, there's a good chance others do, too, and they may be willing to use and/or pay for your solution. Alternatively, after validating the problem and a potential solution, you can build something for someone you're close to that solves their problem. A spouse, family member, good friend, etc. Small frequent feedback loops, and empathy, are key here.
Another shortcut to running your own software business is starting a software consultancy. You can even do this while you have a day job, by hiring other people to do parts of it, or with smaller projects. If you have many of a similar type of customer (law offices, realtors, whatever), you can find the right product that applies to many of them, while being paid to build other things for your client, or this product itself. This is a traditional approach to bootstrapping a software product, and lots of other people have written or spoken about the it and its trade offs.
What succeeds on 'Show HN' and Product Hunt and similar things isn't predictable. It also doesn't lead to instant success, product usage, or paying customers. It's nice I would imagine, people have shown what it meant in terms of visitors and traction, but it's a blip in the life of a product. Having customers that use your product and pay you money would be better, and it's a bit more in your control.
Here's a good link about validating without spending money or building anything: https://www.startupgrind.com/blog/the-startup-framework-to-v...