Yes, NEW content. New, optional content. What is wrong with that? Are players of GTS fragmented if they don't buy GT7 to get all that new content? That's rather how new content works. If they add it for free, great, but I've no problem with paying for genuine new content.
There is a good reason why the payment system for maps, circuits or vehicles has practically been abandoned in competitive online games, being replaced by season passes (Fortnite) or virtual money (GTA Online) and that is that it is not beneficial for anyone.
Anyone who followed the multiplayer online gaming scene 10 or 15 years ago will tell you that paying for extra online content is not productive.
In this scenario, if you are one of the minority that acquires a DLC circuit, it means that you will only be able to play against others who have paid for that DLC, that is, you will not be able to play with many of your friends and in general the effective online population is reduced, which implies that many races will not be filled or that you will have to wait longer to have a full grid and that leads to a vicious circle in which those circuits are less used, which extends the waiting times, etc.
So many people will not be able to access the new content.
Those who have paid for new content find it more difficult to enjoy than free content.
And in general, the abandonment of the online population is promoted, so the life of a multiplayer game is drastically reduced and new DLC will be sold much less.
However, if you add new free content, the online population is easier to maintain in the long term and in some cases grow, and the greater number of active players makes it more likely that some of them will spend money on aesthetic modifications or ways to speed up your progress.
In short, is a much more beneficial system for both players in general and developers. There is a reason why it is the system used by almost all online games today.