How you can argue such things are democratic are beyond me. There is nothing democratic about trillion dollar corporations that can ruin your business for refusing to play their game.
If Google blocks my access to the only viable ad network do you really think it's reasonable to say I need to set up my own ad exchange?
Hackers call every big business they do not like a "monopoly". What's next, Burger King is a monopoly? I dislike Google more than most and would never buy nor sell ads with them, but they have no monopoly on advertising.
> What’s next, Burger King is a monopoly?
I think this just illustrates that you’re not grasping the concept. Of course Burger King isn’t a monopoly. With my car when looking for a drive through dining experience I can go to McDonalds. Or Wendy’s. Or whatever. When operating a small to medium size web site that depends on advertising for revenue the viable alternatives to Google essentially don’t exist.
Situation 2: You want to let others advertise their products or service in your space. There is an endless amount of companies which you can contact to make advertising deals. If you are too lazy to do that and want a third party to take care of it, then you can use Google as a middle man. But they are not obliged to do business with you.
If the justice wants to go after Google, then they could (and should) prosecute Google (and Meta, and Twitter) for all the scam and malware ads they permit through their platform. That is billions of dollars of money laundering, and the CEOs should be imprisoned for this. For life.