I don't think that's true. Even if you think about what was considered junk entertainment decades ago, they still required much more cognitive effort.

Reading about a celebrity breakup in a gossip magazine requires more cognitive effort than hearing about the same breakup in a gossip TikTok:

-You consumed the thing for minutes at a time vs. seconds at a time and your brain had to actively decipher something, not just passively perceive.

-You had to read and couldn't do it while also doing something else, which meant you were more focused.

-You couldn't swipe in a split-second and have another equally stimulating thing that might be completely different, which meant you were more intentional about your mental context.

The medium in which we consume something absolutely matters, independent of what we decide to consume.