I really struggle to come up with ideas that can be built in a reasonable time and tested.
Almost all ideas seem to be executed perfectly.
Its like all niches have been catered to well by existing players
A while back I've read a quite interesting opinion on Twitter regarding that: just start a business. That's it. Literally any business.
As you go you'll start noticing things that could be improved, and problems that want to be solved.
There's some great resources on the right hand side of the Ideas and Validation group.
The best way to generate ideas is to talk to users. Start with what are your top problems or challenges. They will tell you.
Get help with defining, validating and bringing your ideas to life.