The reason is the planned closure of the site that supports Racenet Clubs. This means that after the specified date, players will not be able to create events, participate in leagues and the community, or races based on this system. Racenet Clubs allowed for asynchronous competitions, where participants competed at their convenience. This was one of the key elements of the community, and its shutdown effectively removes the main form of online play for many users.
However, not all network functions will disappear. After July 8, Time Trial, My Team career mode, and quick multiplayer races will remain available.
The changes fit into the general trend of gradually decommissioning old projects after Codemasters was acquired by EA. Despite the fact that DiRT Rally 2.0 still has an active community of fans, the publisher is increasingly shifting its focus to new projects like EA Sports WRC, where similar social functions continue to be supported.