But it's very unlikely the actual product experience would be worse with personalization enabled, measured by probability that a search includes something relevant near the top.
Somehow the Instagram ads algorithm has figured out exactly what I’m self conscious about with my own body; all I see are ads for invisible braces, skin cleansers, and hair treatments.
I don’t actually want to buy any of these things, and they make me feel bad to look at. A de-personalized Instagram experience would be far superior to me.
An unpersonalized IG ad experience would be teenage women's clothing and Netflix branding (assuming you're in the US). You probably don't want that either.
On YouTube, I highly recommend turning off personalization and watch history, especially if you find yourself spending too much time there clicking recommended videos. Without history, it will pretty reliably recommend the same videos again and again, which can help you realize when you have seen a lot and might want to stop.
It may be true that Google has over-invested in personalization-driven features, and under-invested in user-neutral features.
Personalization belongs in the agent. Specifically, the agent that I own and control.
Centralized services have built personalization systems in which they operate the personalization algorithms.
I don't have a problem with that, per se, except in that their interests (profit) and user interests (effectiveness) are only partially aligned.
The biggest reason, as near as I can tell, these system architectures were built is that control of personalization algorithms means (1) a means and reason to collect and retain data on users (that can be used for targeted advertisement) & (2) a means to execute targeted advertisement (via insertion into "recommended" content).
It's likely the only way these services are possible at the "free" price point. But it's disingenuous to suggest that they're the only model by which personalization could be realized.