I disable notifications for most apps on my phone. I've noticed that I spend considerably less time on social media apps after I turned off the notifications. I do have notifications enabled for some apps:
I use Instagram more as a messaging app, and I have enabled notifications for direct messages only.
How to turn off notifications (on iOS):
Navigate to Settings > Notifiations
Click on the specific app's tile in the list ...
and disable notifications!
Here are my settings for Instagram. Click on the Instagram item in the notifications list ...
... and scroll to the bottom of the Instagram notifications settings page and click on the Instagram Notifications Settings link ...
... turn off notifications for everything except direct messaging.
For direct messaging, I only allow notifications for messages.