Monster is definitely a slow burn but I think it makes some of the big moments pay off and feel earned. I think it's peak psychological/philosophical anime.
But when you called an anime from 2004 old school I felt my neck snap completely.
Monster is definitely one of the greats. Most of 2000s and even the 1990s anime are great compared to the 2010s. You'll never, ever get another anime on the level of
Cowboy Bebop. Period.
Then of course, there were the experimental anime like
Serial Experiment Lain, Boogiepop Phantom, and even
Ghost in the Shell. The spin-off series,
Stand Alone Complex, was less experimental but just a lot more confusing with its political jargon. Still a nice psychological series though. And don't forget,
Kino's Journey, an optimistic series that celebrates the beauty in humanity's ugliness, giving us the quote, "The world is beautiful because it isn't."
Higurashi no Naku Koro ni, based on a series of visual novels (or rather,
sound novels), was notorious for its blood and gore and accused of being a mindless horror anime when it's anything but (especially if you've read the novels).
Higurashi Kai, its sequel, showed the emotional core of the novels for the first time, and even then, it was scratching the surface of just how tearjerking the franchise was supposed to be. But thankfully, it also led to other brilliant visual novel adaptations... namely
Steins;Gate, one of the greatest sci-fi anime of all time. Period.
Kuuchuu Buranko, a dark comedy series about an anthropomorphic bear psychiatrist that tackled a bunch of mental illness, including OCDs and social anxiety.
Paranoia Agent, Satoshi Kon's underrated classic exploring the way the Japanese dealt with post-WWII trauma through escapism.
Kemonozume, a horror anime about cannibal monsters with a sympathetic side to them (also see
Shiki, which did the same for vampires).
So yeah, I wouldn't call 2004 old school, but dang, it sure as heck gave us quite a number of ambitious anime and showed us what Japanese animation could truly do beyond just generic shounen stuff like DBZ. It's nothing short of The Golden Age of Anime.
Yeah, you could tell that I have a lot of nostalgia for the 2000s. Barely watched anime from the 2010s because of that. The anime of 2000s really changed my perspective about anime and just storytelling in general, the level of depth and variety one could do with simple drawings. Of course, Pixar movies of early 2000s contributed to that too, so it was really a great time to be an animation fan and be wowed by all these amazing stories exploring a wide variety of styles, genres and topics.