I know you mention not wanting to be a Karen about such matters later in this article, but for this, I always channel my inner Karen (or male equivalent). It is absolutely intolerable, staggeringly inconsiderate, and entirely lacking in self-awareness. I have a zero tolerance policy for it, and here is why:

https://medium.com/blow-your-stack/is-it-ever-acceptable-to-use-a-phone-in-a-cinema-d2b592a3493