Open the Door
I recently read an article called "Open the Door". The author gets asked "how do I start writing", which can be generalized to "how do I have more ideas". The suggestion is that you have to give yourself a reason to have ideas in the first place.
I've felt into this trap myself. It has been for writing but also for programming projects and business ideas as well. My dad once asked me "why don't you start a business? It seems like there's lots of opportunity in software to build something". My only response was that I'd be super down, but that it's not so easy to have an idea. The premise of the article would suggest that I've been going about this backwards.
Writing
Many writers have said that they usually don't know what they're going to write about until they actually sit down and start writing. Moreover, they have to actually sit down and force themselves to write without doing anything else. Even if they can't put a single word on the page, they are not allowed to do anything else. Removing the ability to distract yourself and place all intention on writing makes it more likely you'll find something to write.
Compare this to the alternative: you don't know what to write and so you distract yourself with other things that are not writing. I think if you actually sit down and think about it, you're basically giving yourself to blind hope and divine inspiration. The hope is that you have an idea while doing something else. Yes, there's a chance that reading will spark something in your brain that gives you an idea. But is it likely that you're not reading enough? That you're not doing enough? Put another way, the marginal utility of spending the next 30 minutes reading or doing something else is much smaller than sitting in front of a blank page for 30 minutes and trying to write.
If you want to have writing ideas, you need to open the door and leave it open. That's a precursor.
Programming
I've had a similar experience with programming. For a long time I really wanted to get better as a programmer by going deeper down the stack and doing more systems programming. But I had a block - I didn't know what to work on.
I tried several times trying to find something to work on, that would challenge me and give me more exposure to concepts like memory management, CPU caches, performance, etc. For example, I thought about building a database in a low-level language like Zig or Rust. This never stuck because it was too challenging of a project for someone new to both systems programming and and low-level language.
And I'm here now in the same place. I've worked on some small projects which have been great experiences. But I've lost steam within 1-2 weeks, finding myself wondering what to work on next.
Taking inspiration from writing, maybe I should consider sitting down at my computer and trying to program in a low-level language. It can be anything. Just pick something, and let it rip. The key is that you have to have a singular focus that you're not doing to do anything. All you're allowed to do is program something - anything. Of course, if the idea is to focus specifically on systems programming then it would be a distraction to start building a web application.
So an interesting new insight here is that sometimes it is important to be precise about exactly what door you're trying to open. If you're just trying to write more in general, great, just write. But if you think you want to write fiction, then sitting down and writing journal entries is probably not going to get you anywhere. Training specificity is important.
Business
Starting a business is something else that many hopeful business people complain about a lack of ideas.