Although I agree with your sentiment, I think you are missing one important point. People always preferred shallow entertainment over true art. There is this fabulous quote by Dante that comes to mind:

A voce più ch'al ver drizzan li volti,e così ferman sua oppinïoneprima ch'arte o ragion per lor s'ascolti.

(Purgatorio, canto XXVI, 121-123).

In fact, a sizeable portion of Divine Comedy is just Dante bitching over the stupidity and shallowness of people.

In short: this phenomenon was always there. There were equivalents of TikTok way back in antiquity, for sure.

Yet, we must admit that one does not necessarily exclude the other. At least for reasonable people, TikTok and Rachmaninoff are not competing for the same slot of their time and attention. As for the unreasonable ones, they wouldn't have listened to Rachmaninoff anyways.

What I do find worrying is that the whole spectrum in somewhat sliding either downwards or further apart (serious art becoming too abstract and unintelligible). But that is, at least rhetorically, another topic.