Outside of Plasma Corp it says beta test, and that's the stage it's at right now. Aka - it's the core game-mode that's being polished, nothing more.
This isn't the final product and it'll constantly be updated.
The player numbers dropped because the shop isn't released and it's currently in the testing phase, which doesn't focus on building a player-base, as it focuses on removing issues / minor improvements before we continue with development and add new features.