As for the Greek philosophers, I feel you are being too dismissive saying that they imagined us being more stupid. First, it was mostly about Socrates and second, his position was a bit more nuanced than how you present it. He was concerned about education becoming impersonal, which definitely has some downsides (until today, we haven't discovered any educational mode more efficient than 1:1 tutoring, at least from the student's individual point of view; the economic dimension, of course, differs). Second, he believed that our memory capabilities would go down, which they probably did. We don't have much contact with purely oral cultures now, but the little we do, show that pre-literate people were indeed better at remembering their collective past, including their culture, in the sense of "actually having it in their own heads" instead of "hearing about it once in the class and then promptly forgetting what they heard".

How many people today can recite a thousand songs from memory? Not that long ago, people like that would exist and keep ancient songs alive.

Today I hear Ed Sheeran ten times a day (ugh), but I wouldn't be able to recollect the lyrics even if threatened with an execution.

That is certainly one way of being stupider than before. Yes, it is compensated by other improvements, no doubt about that.

In the '80s movie Trancers, Jack Deth is a visitor from the future, and as he's slicking his hair back with water from a flower vase a woman from the present day asks something like, "People from the future put vase-water in their hair?!" and Jack Deth replies very seriously, "Dry hair is for squids."

Yes, it is possible that tracksuits will become the to-go clothing for funerals and theatres as well as gyms.