what you're seeing now is an alternative launcher for terraria that you have to look up yourself and download separately in order to install mods, it currently has around 32.000 players right now. The original game also has about 25.000.
If the devs are gonna insist on being absolute, full, complete blind retards and lose hundreds of thousands of players by sheer incompetence, then they better make an arcade tab like in dota 2 as soon as possible so that the players themselves can fix the game for them.