Yet as a society, we can definitely legitimately make that determination. And there's no way this Meta's idea will fly unless the EU seriously back off from the core ideas behind GDPR, which has been in force since 2016.
Arguably the biggest point of GDPR is to decommoditize personal data. It does this by mandating that all processing of personal data must have one of four lawful bases. The two relevant ones are:
1. Required directly for the performance of a service. This would mean, for example, that you are buying a medical service, and it is impossible to perform that service without that personal data. In this case, you do not need to ask for consent (as long as there is an agreement for you to perform that service). Many companies request your consent in any case to cover their bases.
2. Consent. Processing of personal information can happen with the consent of the person. The tricky thing here is that the consent needs to be voluntary and freely given. For that to be case under the GDPR, a declination must not disadvantage the person in any way that does not directly and immediately follow from not processing the data.
So it is permissible to show the same amount of less relevant ads without a consent, because that is a direct and necessary result of not profiling the user. It is not permissible to otherwise, for business reasons, to disadvantage the person who doesn't consent. Otherwise it would treat personal information as a commodity, something of value given in exchange for something else, and EU has just decided that is not in its view compatible with the right to privacy. (You must also allow consent to be withdrawn at any time without negative consequences.)
So what Meta could legally do is only sell ad-free subscriptions in Europe for $14/month, and not provide any free tier.
Or it can provide a free tier. But if it provides a free tier, it cannot require consent to use personal information as part of that. It can opt to show generic ads to those who do not consent to the processing of their personal information. Yes, that is less profitable. Europeans are crying crocodile tears. Meta loses the ability to do that which it should never have been able to do, use people's personal information without their consent. It's on Meta to find a business model that both respects human rights and is profitable for them. Or stop doing business if it can't.