PG has said it a million times but start with a problem you have and come up with a solution for it. Chances are if it solves your problem there will be others willing to pay for it.

For example, my wife and I are doing a remodel of our house. We are adding a 300 square foot deck, 2 bathrooms, a storage area, and extending our daughter's bedroom. It is a big project costing about $60k. And yet the project is tracked on paper or through phone calls and texts. Unlike a $30 DoorDash order, I can't log into an app and see where the workers are, what to expect today, if there is a delay, what materials will be delivered, when inspections are, etc. Also, payments are mix of cash or checks, cards to suppliers.

I could build a system to track large home improvement projects, that have all documents like permits, blueprints, material lists on one place, with daily or weekly progress reports, pictures, videos, receipts. Payment could be made through the app, with possibly an escrow service built in. This would solve a big problem for me, and likely others as well.

Peter Diamandis has a similiar view to Paul Graham- Problems are Goldmines.

Terrific food for thought > https://www.diamandis.com/blog/problems-are-goldmines

I think the main issue is filtering which ones are any good. PG wrote an essay which is good http://www.paulgraham.com/startupideas.html

From the master himself:

http://www.paulgraham.com/startupideas.html