Almost all startups are vulnerable initially, like a newborn baby. It's harmless if know-it-alls dismiss your startup. Thinking "there's no way this tiny creature could even accomplish anything" is faulty thinking.

Focus on an intentionally narrow market. It's like keeping a fire contained at first to get it really hot before adding more logs.

Think of startup ideas as:

Your attention to your users should be insanely great, to the point of being obsessive. It is not only the product that should be that great but especially the experience of being your user.

Hardware startups face a problem where they need a minimum order for a factory production run, but don't have the funds. Without a product, they can't generate the growth to raise the money to manufacture the product.

Nearly all startups have to recruit their users manually. You can't wait for users to come to you. You have to go out and get them.

The initial user can act as if they are consultants. Keep tweaking till you fit their needs perfectly, and you'll generally find you've made something other users want too.

Startups take off because the founders make them take off.

You should take exceptional measures to make your users happy. Your first users should feel that signing up with you was one of the best choices they ever made. Then think of new ways to delight them. You can provide a level of service no big company can.

An extreme variant is where you are your software, where you do by hand things that you plan to automate later. It helps to build muscle memory from doing it yourself. It also lets you launch faster.