Mostly because they don't actually hate CoD, not in that they despise it like others do. Trinisete makes a good point that there is frustration involved in the series direction, it's why I stopped playing CoD, because it kept building up the parts I hated about what the series was becoming, so I haven't bought a CoD since the first Black Ops. For them, it still is something they can enjoy with friends and I could even find myself drawn back to CoD if I had a solid group of friends playing it and were asking me to join.
The hate CoD got for Infinite Warfare is insane though. Unrealistically so and was mostly bandwagon hate unseen in even past CoD releases. I personally thought the trailer for the game looked good and the space setting looked kinda neat, even if I wasn't ever going to buy the game. It even has the better song compared to Battlefield 1's choice that better worked with the trailer as I hated the song they picked for BF1, though the editing was good.
A lot of it just comes down to popularity and franchise fatigue. Yearly releases are not great for most games usually, even if they still sell well.