There's no real magic trick.
- You can post it in places where people might be interested, like HN, Reddit, ProductHunt, Twitter, forums, etc. (carefully and thoughtfully, so it doesn't come across as spam).
- You can email it to people who might be interested (very carefully and thoughtfully, with an individually tailored message, so it doesn't come across as spam).
- You can email it to tech journalists, bloggers, and other people with influence, hoping that they'll help you publicize it.
- You can email it to a pre-existing audience you've built up if you're fortunate enough to have one.
- You can buy ads.
- You can produce content or do cross-promotion (which you say you don't want to do--it can work but certainly isn't required).
If none of the above is getting any traction, most likely the product and/or pitch isn't compelling enough and you should iterate on that before investing more time or money into marketing.
- You can post it in places where people might be interested, like HN, Reddit, ProductHunt, Twitter, forums, etc. (carefully and thoughtfully, so it doesn't come across as spam).
- You can email it to people who might be interested (very carefully and thoughtfully, with an individually tailored message, so it doesn't come across as spam).
- You can email it to tech journalists, bloggers, and other people with influence, hoping that they'll help you publicize it.
- You can email it to a pre-existing audience you've built up if you're fortunate enough to have one.
- You can buy ads.
- You can produce content or do cross-promotion (which you say you don't want to do--it can work but certainly isn't required).
If none of the above is getting any traction, most likely the product and/or pitch isn't compelling enough and you should iterate on that before investing more time or money into marketing.