Viewing live theatre, I have no problem shooshing people or telling them to put their phone away. I have occasionally looked right at them and told them to be quiet or I will get the usher involved. I have done that a decent number of times, and I have to say that it has always worked for me. Once at 'On Your Feet', I had to tell two non-regular theatre-goers (I assume) to be quiet twice. The second time, I told them I would get out of my aisle seat and ask the manager to quiet them down. It worked; despite looks to kill at intermission and upon exiting the theatre.
I would not do that in a movie theatre because, frankly, you never know who may have a gun or want to start a fight. Despite that, and cell phones lighting up, I still like to attend a movie in person, particularly if it is a comedy, which I find is more enjoyable to me in a crowd.
Ironically, I find that I don't enjoy the theatres with reclining thrones as much because I don't feel that communal experience. Sitting back, I don't even feel like my wife is there with me, because I can barely see her. It does, however, dramatically discourage talking and you don't see phones lighting up constantly. So, while it should be a far superior experience, it is not for me.
I suspect that I will find a way to attend movie theatres as long as they exist.
One last point: When I am in NYC, I try to attend a movie at the Paris theatre whenever I can because that to me is the ultimate movie experience, intimate, a well-behaved crowd (when there is a crowd), and memories of the first time I ever attended it, in 1966, to see my first foreign film, A Man and a Woman.