No one is saying it's illegal for companies to demand pay as cost of access. What they can't legally do is take your privacy in lieu of payment. So "pay or don't use" is legal, and always has been. "Surrender your data to use" is not, and following that "Surrender your data or pay to use" isn't either.
Because basically everyone giving up all privacy for a modicum of convenience makes the world a worse place. It's a seatbelt situation; people consistently make the wrong decision, so the option is removed. In the abstract it's distasteful to remove autonomy like that, but on occasion we need to make collective calculated decisions like this.
Maybe you'll understand it when I replace one inalienable right with another in that sentence:
"I don't get how it makes me worse off if someone else voluntarily consents to selling themselves to slavery?"
It is much easier for your government to institute a repressive regime if most of your fellow citizens have given up their privacy. Once instituted, the regime can prevent you from leaving the country and harm you in many ways even if you personally were very careful to preserve your privacy.
Although the decision sounds so simple the underlying principle cannot be accepted. Privacy is an inalienable human right, just like being a free person. We, as a modern society, decided that some things are illegal regardless of my much both parties agree to do so. One cannot own another person, or work without compensation, or sell their organs to evade prison time. What EU is saying is that such a transaction is illegal. And just like the slavery, numerous companies are doing everything in their power to keep it.
Same reason you can't sell your organs or sell your physical freedom / time in prison (falsely admit guilt because someone paid you to do so in order for them to avoid prison) or even end your own life. The country you live has citizens who have banded together to created laws and regulations that say these various freedom-y things, if engaged in at scale by people who might have individual reason themselves to do it, are considered harmful to society and so prohibited.
Then... pay for it?