Any time a big change happens to people's daily experience I think it's reasonable and good to have a lot of reflection on if that change is good or bad and what should be done.
For some perspective, the type of person that is going to make a blog post about quitting social media was likely "highly online" in social media spaces and probably doesn't even fully understand the ingrained models of personal disclosure (almost no one does well as the problem is so new) that they realized was unsustainable that lead to them now quitting so they cope by making a blog post. It's ironic and more than a little bit funny.
It's like when someone is new to Alcoholics Anonymous because of legal issues, losing a job, or a partner leaving and they get to step 4 "Made a searching and fearless moral inventory of ourselves." and write it all down and then they instantly hit steps 8, 9, 10.
8. Made a list of all persons we had harmed, and became willing to make amends to them all.
9. Made direct amends to such people wherever possible, except when to do so would injure them or others.
10. Continued to take personal inventory and when we were wrong promptly admitted it.
A drunk would give you a 2AM white knuckled call you don't care about for when they ripped you off 10 years ago, but the action of those steps is the same thing as the drug. I'm not an AA guy or anything but it's a relatable model. If anyone reading is struggling with substance or social media addiction check out SmartRecovery.org for rational group recovery.
So I guess my take on the phenomena of the "I'm leaving" post is that they are the rattles of a person trying to change but the well worn paths to change (steps 4, 8, 9, and 10) are basically the user's DoC (Drug of Choice).
Sure, the posts are self indulgent and suck, but what else do you expect from someone operating with a serious dopamine imbalance?
To answer your question though, it is definitely not "mundane as fuck" to them. One's too many, ten's not enough. Yes, it is the same thing and I gather that you don't likely suffer from it in this context. I think we can all agree that you can just not read their posts
Posts like this even if their content isn't profound or even that novel, that person is working to be a better person and tried to work out their feelings by putting pen to page and yelling into the void.
Your question here is what a lot of people are thinking though and it's a valid question. I'm not trying to cast shade on you at all. Without you asking this question I wouldn't have been able to think about this stuff. Dopamine management is important to a life lived consciously. How we get off differs in a rainbow for each person. Hopefully our discussion here helps someone out in the future. It's basically impossible that it has zero effect.
Cheers.