Marketing is essentially like building a software product. That is the title of this comparison, and here is why they are so comparable.
If you are building a software product, the first thing you have to do is define the niche and your users. You have to decide which group of people will actually use your software product. While you might be able to build some products for everyone, generally that is not a good idea. It is much better to have specialized software for one specific group.
Take the age-old example of a to-do app. Even if you say anyone can use it, different groups have different needs. A to-do app designed specifically for a lawyer is going to look completely different than a to-do app designed for a doctor. Marketing works the exact same way. You need to define your audience, your user group, and the group of people you actually want to talk to and reach.