I used to work on Google Search. I now work on my own startup, which uses ElasticSearch. In many cases, they use the exact same algorithms and data structures, or can easily be fine-tuned to be equivalent. Nevertheless, stock ElasticSearch results are much, much worse, because you start with zero data. To say nothing of not having Suggest, Refinements, universal results, good spell-correction, disambiguation, etc.

I also use DDG when I'm in Tor Browser, and it always strikes me how much worse the results are when I try to do technical searches there.

I've still got my music collection in MP3 form on my hard disk, and it's only an iTunes click away. Nevertheless, when I listen to music, it's all on YouTube now, because YouTube can actually recommend stuff that a.) I like b.) is of a similar genre and c.) I haven't heard before.

I rely on GMail's spam filtering for E-mail to be useful; when I've tried to go back to Yahoo Mail or (heaven forbid) running my own server, the result is just unusable.

You're welcome to try founding a startup that operates as a desktop app and collects zero data from users. With improvements in developer tools and payment systems, most of the ideas from the late 1990s that required millions in venture capital financing could be done by a single motivated dev in a few months. Good luck getting users to adopt your software, though, regardless of how privacy-conscious they say they are.