I believe the mobile app is limited to just studying. Creating new cards and downloading shared decks must be done using either the desktop app or the web app.
I stand corrected. My recollection was that AnkiDroid (the Android app) didn't provide the capability of creating new cards, but I just checked and the current version of AnkiDroid does let you create new cards.
It must be copyrighted or have some other broken dis-economy, because the most obvious product decisions that would make this huge have been rejected.
The whole point of this is to study in spare moments, like on public transit - using mobile. Uninstalled. That's so disappointing because it's so obvious, and I can't trust an ecosystem that dumb.
I didn't think it was possible to be as disappointed in an app as I am with this one.