I also wonder if the aging brain is particularly vulnerable to some of the darker patterns these platforms employ? It certainly seems like it from the small number of data points I've seen.
24 hour "news" is a great example; we leave it on in the background, as Radio or TV, but we're not listening to gain information, we're listening to be entertained - amygdala activated.
With AM radio and broadcast TV, low efforts were mostly limited to 2 hour segments from the 80s-90s; then in the late 90s, cable tv became standard, then in the 2000s the internet (chats, reddit, hacker news), and then the smartphone...
Recently I've had to find things for myself to do in order to make sure my time is better filled otherwise I will "fill" it with doom scrolling. I don't know that my brain is more susceptible (hard to self determine something like that) but my time is certainly more open than it ever was in my life previously.