Hey Jan, glad it made you think. As you've found out it's not easy to rank #1 on Google especially when so few people will link to your product reviews. You need to tackle a specific niche with a focused target audience as a whole and build a community of like minded people around your site in order to make any significant income online sustainably and for the long term.
You’ll also have a better understanding of your target audience’s needs and desires. This is essential since it helps you build trust with your visitors. If they feel like they can rely on your judgment and recommendations, they’ll be more likely to click on your links and make purchases based on your suggestions. Therefore, the best niche will have plenty of potential consumers and will be something you can create knowledgeable and trustworthy content about.