YABU, obv.
I honestly don't understand why do people get their knicks in a twist about it? Yeah, if there's Peppa Pig blasting out of their screens next to your ear - you definitely have a point. Otherwise? If someone's kids, or parents, or grandparents, or all of them together are sitting with their noses in the screens - what's it to you? Did they steal your Iphone or something?
And this bit 'so sad' cracks me up. Sad? That strangers are minding their business and doing their thing? Right.
Incidentally, my own kid doesn't use screens at the table and never did. But it's because she herself never wanted it. I never forbade it. I love gadgets, screens, internet, being online, AI, etc, I think all these are great and we have all the possible gadgets in our home. My DD grew up with devices pretty much since she was a baby. We also do have other hobbies, read books (DD prefers paper books, me - Kindle), travel, go to museums, have friends, DD does well at school and is well behaved. It's not one or the other.