I quit it over 8 years ago. I can only imagine that it's gotten much worse since then.
It was quite spontaneous. I came out of shower, picked my phone and deleted the IG account, FB account (they let you keep the messenger while FB gets de-activated), Snapchat and Twitter all at once.
The feeling of fear of missing out is real and you go through almost a withdrawal period. Things like you launching browser and fingers automatically start typing Facebook's url without realizing and then the browser auto-complete automatically fills in the username and password fields and all you have to do to get a "hit" is to click the "log in" button. But then you have to force yourself to not do so.
Do it spontaneously and remove your account info from the keychain/password manager. Change your hosts file or block it on your wifi router etc. Basically make it as hard as possible for you to get back.
You can also do something like for every second you spend on social media, you need to do that many push ups and pull ups.
The other comment's advice about "seek boredom" is excellent.