When he is at a party and a tv is on in the distance he stares like a zombie at it. It's depressing at how TV changes him and I have to transfer his focus away.
I have a very qualified pediatric occupational therapist friend and when I was sort of bragging about how many "cool things" my toddler can do I was immediately told that they are nice party tricks but don't say much about the development of the child, predict future performance or intelligence, and definitely aren't what I should be focusing on as a parent.
The child didn't just naturally learn to do those tricks. Our games focused a lot on this because I thought "it builds brain and skills", always be ahead of all other kids. In reality only I benefited from this because I could drop it in random conversation and then have pride flow out my ears. And the kid kept repeating the now easy tricks looking for the reward, staying inside the comfort zone.
I was told to simply guide our interactions with a method called "serve and return"[0]. It's a much more powerful tool that makes any and every interaction an opportunity for development, not just individual tasks practiced to perfection and repeated for rewards. You guide but also let yourself be guided so your child gets to feel comfortable opening all kinds of doors rather than you even unwittingly pushing them through the same one again and again.
[0] https://developingchild.harvard.edu/key-concept/serve-and-re...
But I also am very much in the camp of "it doesn't matter what he knows right now. Kids advance in different ways at different times and it mostly just levels out" All you can do is amazed at how fast they grow and try to help them out as much as you can.
Friday was eat-out night when we raised our daughters. A particular Thai restaurant that we enjoyed was crossed off our list because they always had a television on in the corner of the dining area. It was a complete family-conversation killer.
I left a comment on the bill saying that it was off-putting. (I even TV-Be-Gone'd their set on one visit.) But ultimately we just stopped going.
My personal impression is that while there's deffo stuff kids shouldn't watch, the thing that matters is what the kids do apart from TV. If it's nothing, or insufficient, it will be terrible. If as well as screens kids get plenty of high quality attention, the outcome will be good.
You could argue, and I'd struggle to disagree, that less screen time is always good. But there's tradeoffs in this optimisation. Parental attention and energy are also finite - unless you're super rich, have 3 nannies, a chef and not working. At some level, giving the poor overworked parent a break by sticking the child in front of a screen for a bit might mean the parent has more energy to do something worthwhile with the kiddos afterwards.
There's a nice statistical experiment in it no doubt - child outcome as function of screen time, high quality time and "fend for yourself" time, controlled by how much energy the parents have - will the coefficient on screen time be negative? Merely zero? Maybe even positive, just smaller than the other ones?
But good luck getting the data, never mind randomisation.