[verdverm]

The first thing is to understand a problem deeply, where and why there is gap in solutions, and an idea how to solve that. Getting a landing page up helps you validate you hypothesis. You aren't trying to capture users at this point, rather gauge how right your hypothesis is. If it only takes a day as you say, why not do that first? It also gives you a place to quickly add a demo or link to MVP.

In the end, you want feedback on your hypothesis from potential users. A landing page is one way, and nice because it is self service. There are other ways to get feedback as well.

How do you know you are building the right MVP? How do you know you are solving a problem people care about?