What's the long term end goal for society? I think one feature of such a society would be unlimited entertainment available for anyone, which TikTok provides.

I think with most work automated away humans should mostly entertain themselves in person. Art should be increasing interactive as everyone has time to level up beyond passive audience.

> How will showing people short video clips to create a drug like drip of enjoyable chemical reactions in the brain progress the species?

Possibly (pure speculation here): if you carefully observe, at massive scale, how a system [1] behaves, it may provide some insights into how it is implemented. And based on those learnings, iteratively improve how the platform feeds tests and analyzes responses to gain deeper understanding of the system over time.

[1] In this case, "the system" consists of individual human minds, as well as the overall network of minds.

Is there any insight to gain than the already known fact that people will sacrifice long term interests for short term gratification?

I'd bet fairly big $ that there are plenty of them.