Start with the question of whether this will solve a big enough problem for your target audience that they'd be willing to pay for it? In your example case - m

Start with the question of whether this will solve a big enough problem for your target audience that they'd be willing to pay for it? In your example case - most likely not. The problem is there, but menus going out of sync on delivery apps probably doesn't generate enough troubles to be worth paying for. Follow-up with if they will be willing to pay, how much? Then take that number multiply it by the audience size and see if it's worth it. These two questions tend to eliminate the vast majority of half-baked ideas very quickly.