I have to agree with you about Bird Box, it is not as special or as amazing as everyone tried to convince others that it was. Especially on social media.
I believe the hype was mostly people wanting to be in on all the free promotion social media platforms were giving anyone that talked about it. Most probably never saw the movie themselves, relying on the plethora of posts to get an idea of what it was about, what to say, how to react to comments.
I know less than 6 months after it was released the popularity shifted and more and more negative focused posts started gaining traction. Some people even flip flopped with their opinions of Bird Box, completely ignoring how they almost lost their minds at how amazing it was and calling people out for not having seen it.
Bird Box went more viral online due to the people that must follow whatever is hot than it did for its quality.