MCU started flopping becasue they put out a bunch of bad content. DCEU flopped same reason. SPUMC likewise. All largely unrelated to each other’s failures.
Joker 2 doing terribly so far is unconnected to any of them — joker 1 perfectly connected to a certain moment that isn’t there are more, didn’t need a sequel, and they made a big anti fan change in direction.
Reeves stuff is separate, will stand or fall on its own (Batman 1 was medium performance and expect th same for bat 2). DCU is a new start, will stand or fall on its quality mostly. MCU future will stand or fall on upcoming MCU quality. Etc etc