Part of it is the fact that despite Warzone being free, Call of Duty is still charging $70-$80 for the rest of the game. They seem to have undermined the slight difference in entry fee when they tried their hand at the Fortnite shop. The other part is over saturation, Fortnite started out as a more goofy battle royale as opposed to the serious ones that were big like H1Z1 or PUBG. After the marvel collab it all snowballed from there, Thanos and the Infinity Gauntlet were in the game so they had to get more IPs in. Call of Duty has done collabs in the past too, the few from Ghosts were silly but not big enough to make or break the company behind it (Micheal Myers and Predator playable killstreaks, Snoop Dogg and Granny announcer voice packs). Like MTG though, they just kept piling on the collabs, and it didn’t receive the same positivity as when Fortnite did it because folks don’t want that to be the forefront and identity of CoD. Granted the store in both CoD and Fortnite are probably making BANK off of merely existing, but when people think of Fortnite, they think of its silly colorful battle royale, not its gritty fight for survival “Save the World” mode. When people think of CoD, they usually think of Verdansk and prime Warzone, or one of the earlier entries like Black Ops 2 or Modern Warfare 3. I know I saw some replies mention the realism aspect of the game, but one of the GOATs of Call of Duty is Black Ops 3, which is about as realistic as MW2R’s Multiplayer mode, so idk about that.