I get your point with blockchain(altough i'd like a source for 2% of the entire human energy production going into it) but ads are useful actually, they make people know about what other people do which drives economy, and economy is basically a fancy word for the system that distributes each human's limited time into the various tasks society needs(which do include large scale planetary development but also for example, your local supermarket which makes you eat).

As for tiktok and silly dances, humans don't need only food and water to work reliably, they also need mental health. So leisure, amenities, relationships etc.(yeah tiktok included) are an addiction in the same sense food water and oxygen are an addiction, we just need them to work.(obviously while "addiction" to leisures is in general not a real problem, addiction to a specific thing in this list is, just like addiction to a specific food is a problem. I'm not saying tiktok addiction is a good thing)

If you think humanity's purpose is to develop their knowledge of the universe and techonological grasp, then i reassure you that(almost) everything we do on this spinning ball is a cog in the machine that ultimately sustains that development