In this excellent 2012 essay, Paul Graham explores the paths to the best ideas in Startup.
The all-too-common mistake of founders who seek to solve problems that no one encounters, favoring a smaller number of highly motivated users to a large number of less committed ones, the difficulty of projecting beyond a niche market, the advantage of being able to implement a first version of an idea oneself, the importance of favoring multiple fields and disciplines in one's personal education, the overestimated risk of competition, the bias that prevents us from looking at problems that are tedious to solve or those that we despise.
The topics covered are numerous, the post is full of excellent reflections. It is a very rich article that deserves regular reading.
One of the biggest dangers of not using the organic method is the example of the organic method. Organic ideas feel like inspirations. There are a lot of stories about successful startups that began when the founders had what seemed a crazy idea but "just knew" it was promising. When you feel that about an idea you've had while trying to come up with startup ideas, you're probably mistaken.
When searching for ideas, look in areas where you have some expertise. If you're a database expert, don't build a chat app for teenagers (unless you're also a teenager). Maybe it's a good idea, but you can't trust your judgment about that, so ignore it. There have to be other ideas that involve databases, and whose quality you can judge. Do you find it hard to come up with good ideas involving databases? That's because your expertise raises your standards. Your ideas about chat apps are just as bad, but you're giving yourself a Dunning-Kruger pass in that domain.
The place to start looking for ideas is things you need. There must be things you need.