How do you actually find app ideas that can make even modest MRR as a solo indie dev?

I’m a solo iOS dev and lately I’ve been struggling way more with finding the right idea than with building.

I know this probably sounds naive, because yes — I know it’s hard, and I know there’s no magic formula. But I keep seeing people talk about “simple apps” doing decent MRR, and I honestly can’t tell if I’m approaching this the wrong way, looking in the wrong places, or just overthinking everything.

For context: I’ve already shipped apps before, so this isn’t “I have an idea but can’t code.” I know also how to actually code, not just type "BuIlD mE aN aPp!!1"

My problem is almost the opposite:

I can build.

I can ship.

But I keep getting stuck at what is actually worth building.

One of my ideas actually did turn into a real app — an app for bottle deposit return points in Poland. And I still think it was a genuinely good idea. It solved a real problem, it felt useful, people got it quickly.

But if I’m honest, it was never really designed as a strong MRR business.

It’s more of a crowdsourced utility. The monetization was always weak by design — more like tips, with a small subscription addon that doesn’t really drive the whole thing.

So now I’m stuck in this weird place where I know I can spot real-world problems sometimes… but I’m not sure I can spot the kinds of problems that make for a good small indie business.

What I’m looking for now is something that:

- a solo dev can build relatively fast

- has a real reason for people to pay

- doesn’t require some giant startup setup

- could realistically make even modest revenue like $100–500 MRR to start

I’m not chasing “build a unicorn in a weekend.”

Honestly, I’d be happy with one small app that just works as a business.

What messes with my head is that other people seem to find these ideas, validate them, ship them, and somehow I keep bouncing between:

- ideas that are too broad

- ideas that are mildly interesting but weak monetization-wise

- ideas that sound trendy but probably won’t convert

- or niches that already feel too crowded

So I guess my question is:

How do you personally separate “this is a real problem” from “this is a real business”?

And when you’re a solo dev, what signals do you trust most when deciding an app idea is actually worth pursuing?

I’d genuinely love honest answers — even if the answer is that my whole approach is off.