> But again, this wasn’t easy. Especially for us who don’t have the expertise in some vertical to understand its problem enough to build a solution for it.

I am not sure if this is necessarily true. You can spend a weekend studying and understanding a vertical you want to build for.

You can start with questions like "what are some of the pain points this vertical has", come up with ideas, test those ideas and make a determination if your idea is worth pursuing.

Should you pick a niche, yes I think this is necessary. For example, instead of focusing on trying to fix the internet for everyone, focus on solving issues in the UI/UX world for example.

Hope this helps.