According to Marvel Rivals director Thaddeus Sasser, Concord's problem was that it "didn't bring any unique value" to players, which is a hair harsher than we would put it. Still, we suppose Sasser would know,

Marvel Rivals game director Thaddeus Sasser has suggested that Sony’s Concord flopped because it “didn’t bring any unique value” to players. Sony took Concord offline and pulled the game from sale within two weeks of its release this summer, citing a poor reception from players to the live service shooter, which was priced at $40.

The instant success of Marvel Rivals months after the disastrous launch and shuttering of Concord has players debating Sony's strategy.