The Guardian covertly sends your data to 58 tracking services

At least the Guardian isn't a Putin operation.

I co-run a network of websites that are ad supported. We'd consider our network to be quite optimized in terms of maximizing ad value. If you're unfamiliar with online advertising, 58 tracking services sounds like a lot. To me that just sounds like "optimized" header bidding -- ensuring you're (the publisher) getting the best value for the ads you're displaying. Google does a ton of work ensuring malicious content is not being served, but of course the transfer of user data (which could be considered malicious) is fundamental to their business model, as well as the business models of every company that serves ads to their users. And it's the wild west where that's concerned -- whoever can make the "best" use of the data will pay the highest price.

This is why GDPR is catastrophic for ad-based EU business.

Realistically, if 58 tracking services watching what you're doing is scary to you, you'd better be prepared to either: a.) pay your worth or b.) see many of the sites you use go out of business or have their ability to operate severely diminished.

I just use uBlock. I can't remember the last time I saw an ad on a website.

Self-hosted analytics like Matomo tell you who visited your site for how long and from what IP address and what country, etc. But is this the only reason that people run trackers? I thought people ran trackers for the following reasons (in addition to analytics):

(1) To get targeted ads, and thereby money because you showed a targeted ad. So if the Doubleclick tracker you embedded on your site sees that your visitors are watching lots of dog videos, they can serve you ads for dog food. I suppose (in theory) you could not embed the Doubleclick tracker and instead send Doubleclick the info you collected with your own self-hosted analytics, and get Doubleclick to send you the dog food ad which you insert into your site yourself.

(2) To improve ranking on Google search. I've read that running Google Analytics improves your search ranking as opposed to letting Google simply crawl your site.

And other reasons too?

I welcome any corrections if I'm gravely misunderstanding the technology and motivations.

In which case see the last part of the post you replied to.

I personally don't mind if web advertising phases out. I have no idea what the alternative is, but web advertising has become a cesspool of privacy invasion and coercive commercial intent that the world is better off without. In this day and age you might imagine that nothing exists in the world but commerce and advertising for that commerce, and without it no one would publish anything. But it's human nature to communicate and share stories and ideas, and if the web advertising industry fell out from under publishers, the web would still exist.