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not unpopular. having your phone up taking pictures or recording/streaming video THE ENTIRE EVENT or a significant portion of it is not fine.
I hope someone holds a screen up that blocks your view, at every event you go to. >

I hate to break it to you but a phone screen won’t block your view >

Numerous phones, and the hands holding them, can quite easily block the view.  
The last concert I went to, I could see the artists on stage for less than ten percent of the duration of the concert. It's incredibly inconsiderate. >

I think it's a popular opinion to be honest