For example, I'm about to list my house on the market. The real estate agents who reached out to me last year and the year before that to try to induce me to sell the house had no chance of succeeding. Now is the time if they knew the secret that I'm about the list the house that they should all be competing for my business. The only relevant piece of information is that I'm about to sell the house. That is a valuable lead that many in my region would bid on. My background information is frankly not that relevant to the value of that lead, and isn't something that is readily surfaced by the kind of deep profiling that is supposed to be going on. It can be signaled by me signing up to some kind of list that sells my lead to a zillion people at once, but is never going to be surfaced accurately to the people who can earn the most profits from it by my Youtube habits or whatever.
Zillow sells the logged in user data in the market I'm buying in to the real estate agents listing the houses, but that again is not something being modeled by some kind of big data operation, but is merely the same kind of "little data" provided on things like dating websites or LinkedIn when people browse your profile. There's no modeling going on there that requires sophistication.
And from what it seems to me, there is a giant bubble. The vast majority of companies doing "data science" jobs are things that a smart undergrad can do with a month or two of training. And this is because I believe C-suites have completely gulped down the data is oil mantra. There are entirely charlatan companies with unicorn, even decacorn valuations now being built on this mantra - for example, CRED in India.
Yet, as you said, and as I believe too, most of the data is worthless.