I'm afraid your knowledge is a bit out of date. Even Flynn has given talks about the "reverse Flynn effect" in the past three decades. IQ scores have been going down.
My suspicion on this is not the noise from the device, or even the devices themselves are the problem... It's that we sit on our ass all day watching/listening to them. Brain health is correlated to exercise and movement.
Recently: https://www.sciencedirect.com/science/article/pii/S016028962...