So what? Those people use Facebook because they like to do so. If you feel like Facebook treats you unfairly then stop using it. It is permissible to communicate with people that use Facebook even if you don't use it. If you fundamentally disagree with the way Facebook operates then stop using it. Just stop using it.
That supposed blurring is illusory. There are no impactful consequences for not using Facebook; it is wholly unimportant and an entirely superficial distraction, in fact, less use of Facebook correlates positively with mental health. You most certainly do not need Facebook to operate in society.
> When you enter a new peer group of 20+ people you can't just tell them to completely mix up their habits because you happen to not like what they're doing.
You're constructing an image of reality that isn't correct in order to support your position. If you encounter a gathering of your peers and someone says, "hey, you on Facebook?" and you say "no, I don't really use Facebook" in reality, the conversation just moves forward with a discussion of a different communication medium like SMS or snapchat or twitter or e-mail or whatever. The suggestion that lacking a Facebook is social suicide is obviously wrong.
Perhaps in your particular friend group people only communicate through Facebook, but that is definitely not typical and it still doesn't mean you need Facebook, it means that you find the Facebook network convenient for communicating with a particular group of people. Participating in a group-chat is not a necessity. What if your entire friend group communicates on Discord, does that mean you need discord? Obviously you don't need it, you just find it convenient. If you refuse to use Facebook and none of your friends care to adjust their habits to communicate with you that really has nothing to do with Facebook and certainly doesn't imply that Facebook is now a social need.
> The thesis you're defending is wrong.
My thesis is just common sense. The idea that Facebook is a necessity is laughably absurd.
Even if those two platforms die off before they reach the tipping point where most would agree membership on the platforms are necessary to operate in society, we should still realize this is a potential eventuality. If you disagree with the core point of this potential outcome, then I'd be interested in the argument, but it certainly seems possible (and I'd argue, likely) that Facebook or a site like Facebook could quickly evolve into something that you need to be connected on to conduct business, interface with the government, get a job, get into school, or in general be connected to society in a way that is not making you "sub human" in a future where the whole world is continually connected via the Internet at all times.
If you make something addictive, people still hold personal responsibility and can decide to quit, HOWEVER the majority of people will still find it hard to do so and therein lies the issue.