1. Tutorial or Articles - Everyone needs help. Creating tutorials on your website brings users but doesn't add much interaction. Then the new enhancement from IPS kicks in. I am just going to quote you @Joel R -
2. Log-in - Make it fast and more user friendly. Add all available logins ex. Twitter, FB, Discord, etc etc. Time is important and everyone hates filling Govt. forms. :P
3. Target advertising or follow ups - Can't wait IPS to add Bulk emails/PM's which supports Custom Field. Don't spam users with generic emails. Everyone hates it and it would be soon marked as spam by user! Ex - If player is not playing RPG games - don't send RPG games email. Use custom field which they have selected i.e. FPS to send him FPS games update. I can't wait for new enhancements on it! @Matt
Use custom fields to show their profile completion progress, Registration should be email/password and validation.
4. Themes - Provide light and dark theme at least. Even now mobile OS provides - light and dark theme so that user can use what they like. I just wish Themes would be available to select through drop down menu rather then all the way in bottom!