To be honest I only notice that with movies. Books are fine, TV show episodes are usually fine, but long movies I can have a hard time concentrating on. Maybe because I can easily change my reading speed to keep my mind occupied.
It would be easy to say "today's movies aren't as interesting as the ones of 20 years ago" but that would be ignoring that I changed in those years - namely, I've seen a lot more movies and read a lot more books and watched a lot more TV.
It would be unsurprising for someone to say "not everything I liked at first still holds up today."
But I apply the same reasoning against my forward-looking watching/reading: "I've seen so much more now that fewer things impress me at first, as I have so much more to compare with."
So a book that's only mildly capturing my attention? I can speed up my reading, skim a bit more over the uninteresting parts. A movie? So much harder!
I can't say I really regret this change, I haven't noticed any real downsides. There's too much content and not enough time these days.
I think Movies just suck because TV shows are where all the good production is happening.
Making a good and compelling movie is really really hard, and now you can just churn out superhero stuff and make millions or do a TV show and have nearly none of the constraints of cinema.
The 90s was an odd period with countless great movies and massive budgets.