First, we need to agree that "A great product will speak itself" is total BS.

But, in order to outpace millions of other apps in long run, we need to perform the following

1) ASO App store - So that our apps are searchable with the right keywords

2) Localization App store - So that our app can reach more users

3) A/B testing App store - So that we will find out what is the most effective graphics asset

4) Paid advertising - So that you will get real users

5) ... (other marketing activities)

As we can see, all the above activities require a substantial amount of money (We need to hire people with the right skill to complete the task or pay our ads network)

I think knowing how to spend the marketing money the right way, is the key to success in Google Play/ Apple App Store.

I am still learning the hard way, though.