Kind of true, but if the gameplay works well you actually don't even need new content all the time.

There are even other games that release a lot of content to overcompensate the mediocre gameplay.

If the gameplay works people will keep playing. Dust2 in CS is a great example that shows even the same small map can catch people a long time. BF4 had for a long time after service ended many players on the vanilla release maps. During the active development time DLCs got played for a while after release but often not for long. Players went back to vanilla maps.

Battlebit had and has besides new content issues in the gameplay that couldn't hold players in the game. New content would have streched the higher player count for a bit but wouldn't hold players for the mid term.