The Killing Joke is probably the most singular example of everything wrong with cape comics.
For one, Moore's mediocre writing is the worst part of the comic. Moore himself has admitted to this, and has disowned the story in the past due to his own one-note, flat work. Despite this, it's always MOORE's The Killing Joke. Not Brian Bolland, the master of iconic and beautiful covers, making a pitch perfect foray into interiors without sacrificing his own personal style or competent aspects of comic storytelling, unlike a certain cover/fanart painter whose interior work is trash. Higgin's, the Michael Collins of Watchmen, psychedelic and experimental colors are usually never even mentioned, but I'll get to that.
Then you have DC itself, who have abused this decent pile of adequateness so much that it's literally unrecognizable in its current published form, aka the Deluxe HC. That, on top of the rush to make the events of the comic "canon" due to its popularity, which changed nothing besides crippling Barbara. Actually, if another thing changed, it was the occasional garbage DC writers creating "tragic" Joker since 88, in an attempt to hijack Moore Magic. Even though it's been almost 30 years, DC is still pillaging the legacy of nothing for all it's worth, with an animated adaptation that saw the Timm being paid to essentially commission a whole team of animators to bring his weird, powerplay slashfiction to cinemas across the world.
Finally, totally unrelated to the quality of the comic, but still important to mention while discussing the comic, is the way people have latched onto it. Everyone from Tim Burton to that guy you knew in high school who always talked about "graphic novels, not comic books" LOVES The Killing Joke. It's the BEST Joker story dude, cause it like shows, that like, everyone is just ONE BAD DAY from like, you know? Bro.
TKJ is writer-centric, corporate prostitute, and crippled pussy on a pedestal trash.