Article 4.11: ”'consent' of the data subject means any freely given, specific, informed and unambiguous indication of the data subject's wishes by which he or she, by a statement or by a clear affirmative action, signifies agreement to the processing of personal data relating to him or her”
So there should be little need for mandatory boxes.
Using the GDPR to go after one big player that seriously screwed up is one thing. I certainly wouldn't be comfortable if I held Facebook stock right now.
But going after all the big players, just for not complying with something that is probably impractical for any of them to comply with, is something else entirely. How long do you think public sentiment is going to support government regulators and the GDPR if the likes of Facebook, Google Mail, WhatsApp, Instagram and SnapChat all go dark across the EU for an hour, or a day, or a week?
There's nothing unreasonable about it, it's the plain reading of Article 7 (2).
Regarding the big sites, I don't see how is that relevant to your initial point about whether "every site" will have mandatory checkboxes, and so I'll let someone else read the magic 8 ball.
Like the article says, there might be a way, somewhere deeply hidden in the website to revoke the consent, but do you really want to spend half an hour for that (if the button really, exists, and if it actually does anything)
A non-functional link is also a GDPR violation.
That said, I agree in general: it's a burden on me to make these websites respect my rights, and that's kinda bullshit. I either have to go through the hoops the site sets up, or I have to go through the bureaucratic hoops of the organization that judges the hoopiness of the website's hoops. But if I do care enough, there is now a stick to wield, which is an improvement.
"It shall be as easy to withdraw as to give consent."
It used to be that the GWR train Wifi would automatically log me in. But now that has changed, and it takes me to a pre-populated log-in screen, which requires me to untick the "Add me to the mailing list" button, and tick the "T&Cs" and "Privacy statement" buttons.
I suspect that this is a GDPR hoop to show they have consent for every bit of data they use. But all I have to do is forget to untick the "Add me to your mailing list" button once...