The current world operates on ironic, detached repetition of memes as "facts", which take prescedence over the "truth". You may repeat those "facts" as much as you want without caring, while those who defend the "truth" are revealing their legitimate engagement and are thus vulnerable to ridicule in comparison.
So, Kingdom Hearts.
Truth: KH's story is told through a linearly released series of games
Memetic "fact": Nomura puts lore on literally anything such as cereal boxes and you have to read all of it!
(Note: This is largely spawned solely by the short audio scene from the concert. However, nearly every single Japanese franchise ever has included drama CDs where characters have conversations about as unimportant as that audio scene, just filling in a convo we know happened from context clues as a treat for the fans. This is not unique to Kingdom Hearts or notable.)
(Note 2: If the mobile games do not get turned into console games like coded did, this makes the first claim untrue; however, people practically fall over themselves defending gacha games and MMOs in other series, so I don't think people actually care about this.)
Truth: Sephiroth appears as a bonus boss in KH1 and 2, mostly separate from the main story
Memetic "fact": This is a game series where Mickey Mouse fights Sephiroth, that's so ridiculous!
Truth: KH is a series of action-RPGs with different titles fitting to their contents, telling a story that meanders through different points in time
Memetic "fact": KH expects you to play all these spin-off side games with completely different gameplay and nonsense titles to understand the REAL games
Truth: Kingdom Hearts was the only series Nomura was allowed to direct until FF7 Remake, so he includes his personal expression in it
Memetic "fact": Nomura largely made all the FFs he did character design for, yet insists on forcing his personal expression and OCs into Kingdom Hearts
And of course there are many other ways to show your detachment from KH without directly stating a falsehood. For example, KH's choice of worlds, although limited by what's owned by Disney, emphasizes worlds based on fairytales or children's literature to drive certain themes, but people who would never engage with this in their lives will joke about all the wildly unfitting things they think should be in KH next, because it's all a big joke to them.
Also, Kingdom Hearts makes an especially good target for this due to its perceived popularity and seeming naivete (which isn't exactly accurate), but a lot of these attitudes apply to other story-based Japanese game series too - a general hostility against a director perceived as full of himself for arbitrary reasons, a sense of indignation at the idea of following a story instead of just skipping to the newest entry. In the 00s (when KH began and was at its height of popularity), it was considered natural to talk about how Japanese games made no sense and all their writers were on drugs for expecting you to care about the story of a video game at all. Though even people who will gladly surround themselves with JRPGs often look down on KH.
EXTRA BONUS ADDENDUM: Although the Kingdom Hearts story truly does become in need of rigorous scrutiny to interpret in works such as UX, this is definitely not what people who joke about the series being impossible to follow are talking about, because nobody has read UX except for like, half the people in KH-specific communities (much of its implications have barely taken). The jokes about it being impossible to follow are 100% still hung up on "TWO ANSEMS?????", and will never progress beyond that point.