Same as with any addictive thing, you can use and you can abuse. And the change isn't instant.
You can play MMO socially in a guild, or you can simply grind max levels / rare items endlessly.
You can play an IAP and ad-riddled mobile game to kill some time when waiting in queues, or you can have it become a part of your life checking the game everytime you have a minute of downtime.
And the transitions between those states happen impreceptibly, and there is no defined line beyond which you may consider the activity harmful.
You can play MMO socially in a guild, or you can simply grind max levels / rare items endlessly.
You can play an IAP and ad-riddled mobile game to kill some time when waiting in queues, or you can have it become a part of your life checking the game everytime you have a minute of downtime.
And the transitions between those states happen impreceptibly, and there is no defined line beyond which you may consider the activity harmful.