From Facebook's announcement:

In the JavaScript community, engineers share hundreds of thousands of pieces of code so we can avoid rewriting basic components, libraries, or frameworks of our own. Each piece of code may in turn depend on other pieces of code, and these dependencies are managed by package managers.

Exactly. That's the problem.

From NPM's blog, acknowledging the release of Yarn:

Today, Facebook announced that they have open sourced Yarn, a backwards-compatible client for the npm registry. This joins a list of other third-party registry clients that include ied, pnpm, npm-install and npmd. (Apologies if we missed any.)

Trying to solve the dependency management problem by adding another layer of dependencies to the equation is as stupid as it sounds.

From an outsider that doesn't do web development for a living, this is crazy. I don't know how people cope with the web ecosystem. Specially the front-end part.

If you're a web developer, my condolences.

P.S.: this article really resonated with me, as I've been spending some time doing web development for the past few weeks.