Why is it so damn difficult to come up with good project ideas that’s actually useful for other people?

Because everyone else is also trying. Limited bandwidth of useful ideas.

Build an app for people in telecoms that can do linesman's equations, unit conversions, throughput calculations, etc.

@milkybarkid Oh, and put a Cisco logo somewhere, guaranteed hit

Maybe you should make project about helping others to figure out theirs useful ideas :).

Rule number 1 of entrepreneur. Where others see problem him/her see opportunity.

Rule numb. 2. Find something what works but it is shitty and make it better.

Call me once you are billionaire. I want my cut for this advice:)

Just joking