I expect the EU in general won't stand for it though as too many people will make the 'wrong' selection.
You can't go "Ads + Tracking" or "No Ads + No Tracking" there are 4 options not 2.
Facebook's issue might just be that their entire ad platform is instead built around personalized ads. Revamping their ad network to do well with content ads might not be worth it. Especially since that would cede ground and might compel other jurisdictions to force them out of personalized ads as well.
In a voluntary society, both parties must consent to the arrangement for a user to (freely) use a service.
So for use cases where you need the user's consent because you don't have a different GDPR-valid reason for processing data (many reasonable use cases don't need consent, but user tracking for advertising generally does), that processing is permitted only if that consent is freely given i.e. willingly 'gifted'.
One way how it's implemented is that if some service if conditional upon 'consent' then there is literally no way to get 'GDPR-valid' consent - the user clicking 'I consent' to bypass a paywall doesn't count as the user consenting, and neither does signing a personalized pen&paper contract saying that the user consents to tracking in return for getting free use of some service, because that's not "freely given consent" and so it doesn't permit Meta to track that user. It's just like signing a contract where you get $10000 in return for agreeing to be enslaved for some time - your freedom is not something that can legally be sold, and so are the privacy rights.
The other way how it's implemented in GDPR is that it must be possible to withdraw consent at any time (including 5 seconds after signing up to a service) without any adverse consequences such as the service being cancelled or increasing in price. Obviously that's not a problem if the consent is freely given, but if someone tries to figure out some roundabout way of buying or trading for consent, the consequence-free cancellation makes the point that it's not supposed to work that way.
Of course, companies are not required to provide any service, and they can require a fee for some services - however what they can't do is buy 'consent' with discounts or free service; the GDPR limitations to tracking users are intended to apply to all tiers of users, no matter what Meta does or wants to do. Meta can gift users free service; users can 'gift' Meta consent to tracking, but they can't make a binding contract on that because under GDPR conditional consent is literally meaningless and worthless.
Is that actually illegal? Or am I missing a difference with what you're describing?
The other is that GDPR is still 'enforcement-limited', and there are many organizations that simply violate GDPR - the fact that some organization has done something for years and has not yet been forced to change their ways does not imply that what they do is permitted by GDPR; it's just that the enforcement of GDPR for the trickier parts like online services (as opposed to the important services in physical world, employment, real estate and renting, banking, telecommunications, medicine, etc which were prioritized and are now highly compliant) is starting with the larger violators like Meta, other companies would be handled afterwards, and since news companies are 'politically sensitive' I'd expect that lemonde.fr would be among the very, very last on the regulator's list.