Ease of access to the thing you're addicted to is a big factor for relapse probability. That's one reason why it's so hard for people with food addiction to lose weight. Developing self control is a lot harder than you make it seem.
But developing self control isn't impossible, else EVERYBODY would be "addicted" to all manner of things - alcohol, smoking, food, sex, shopping, hoarding - all of them.
As these things aren't experienced by everybody, there must be a possibility that self control can be cultivated. It also is supported by laws that punish you for lack of self-control: murder in the case of rage, stealing in the case of greed etc.
In all cases I am sure the addiction-help courses encourage you to not use/take the thing you are addicted to. They are pushing towards self control, else it'd be a pointless thing to undertake.. In this case it's totally possible to just not use the app - uninstall it, or don't launch it, or don't pick up your phone.
Buy a cheap smart wristband and only enable important notifications to cut out the noise?
I wonder if lack of notification lights is anything to do with it? About 20 years ago the Nokias etc. had notification lights and even the early Android phones had them, which meant you knew to look at it as it gently flashed. They seem to have fallen out of popularity and so people now look at their phone all of the time just in case there is something they have missed, and then develop a habit of looking, which only gets worse and worse. You end up training yourself to do the habit, just like biting your nails, or a nervous tick where you scratch your head at certain times.
If the phone was off all of the time until something actually important happened (ie a notification light), or you developed the skill to only look at it at set times throughout the day perhaps that'd help.
If not, then surely ALL apps need a "take a break" feature built in. I mean, I could be spending way too much time inside Notepad... or YouTube... or VLC...
Is Notepad, YouTube and VLC to blame if I spend all the time looking at them??
Or is it my fault?
Perhaps I should take responsibility for constantly using Notepad, YouTube and VLC instead of blaming the app.