The "Mirror Any" proxy configuration works for defined repositories. It supersedes, but does not hide, the built-in central and snapshots repositories, unless overridden by the user.It defines a coarse-grained proxy rule that does not differentiate between releases and snapshots and relies on the defined repositories to do this resolution filtering.
Our recommendation is to use 2 virtual repositories in Artifactory (not a must, you can use required repo only), the first will aggregate all release repositories and the second will aggregate the snapshots.
Then, configure your settings.xml file with the mirror as follow:
Please note: Artifactory can automatically generate your settings.xml. Please read more about this here.