Embedded libraries that never get updated. That may expose security vulnerabilities. Different apps including those different versions of libraries. No. That's not progress. That's ridiculous.
Not all of the libraries you use are embedded. Only the ones you need that aren't part of the platform you're targeting are.
For example, if you're building an app on the GNOME 3.28 platform, it would presumably include (for example) an SSL library like OpenSSL. Now, whenever the platform is updated (3.28.x), all of the apps that target that platform (presumably all of them) will get the updated OpenSSL for free.
And if an application really needs a specific version of OpenSSL, then at least you know it's sandboxed, which is much more than you'd get on almost any desktop Linux distro today.
From the website:
"Dependencies that aren't in a runtime can be bundled as part of the app. This makes it possible to use dependencies that aren't in a distribution, and to use a different version of a dependency than the one that's in a distribution."