Advertising is an intentionally complex system so that companies can clip the ticket at multiple stages throughout the process. Google should be broken up, but the whole ad tech system needs to go into the bin if these problems are going to ever get fixed.
https://www.forbes.com/sites/augustinefou/2021/02/15/how-muc...
Some companies like Google are incredible at this. Google is not a "monopoly" in this space. In fact the world has far too many Google equivalents but absolutely no one comes close to Google in generating top dollars for publishers. I am saying this after working for 10+ years competing against Google.
But since Google is playing both sides and has so much sway over the market, they're able to manipulate things. Even if they're not manipulating things to their benefit, it's still not great to have a single party have so much control.
There's certainly some tension between advertisers and publishers, in that advertiser would like to pay less and publishers would like to be paid more; but there's a lot of things an ad exchange can do that are good for both. Selecting ads to display that result in meaningful downstream conversion is good for both advertisers and publishers, because they'll both get paid and maybe something about the user getting something they want too.
Showing inappropriate and ineffective ads isn't great for the advertiser, and it might make the publisher money in the near term, but it can drive users away and tends not to be sustainable --- advertisers stop advertising in venues where they don't get results.
The value of a good ad exchange for the publisher and the advertiser is when it provides reasonable matching at a lower cost than the parties arranging advertising directly. Possibly some amount of assurances for both sides too --- the exchange should ensure the advertising code and destinations aren't going to compromise the publisher or their user and should ensure that the ads paid for are actually seen (to the degree possible). There's room for the exchange to profit from scale while still being lower cost than self-managed advertising.