Having just replayed it, I definitely think RE4 is where the series as a narrative went completely off the rails in terms of what I was looking for. From the focus shifting from semi-believable corporate bio-experimentation to full scale secret European parasite cults to the awful characterization of formerly respectful, understated Leon as a wise-cracking ladies man, it just veers completely shamelessly into all the worst trappings of bad big budget film storytelling.
It's also very much of its time in a way that does not do it any favors. The fixation on US interventionist policy and American hegemony and preoccupation with "government agents" is completely informed by the Bush-era war on terror climate and feels very antiquated now, whereas Re1 & Re2's general themes of corporate scheming, bio-tech experimentation, and shadiness within more localized governmental/law enforcement agencies still feels relevant and engaging. I think that part of the underrated charm of the original game was the leveraging of a scope that was both worldwide in significance but very local in flavor. The player felt like they were unearthing a story that reached beyond Raccoon city, but the trappings of the town itself made everything feel hauntingly insulated. All the touches of rural life also informed the games initial aesthetic and gave it a touch of eccentricity that evoked Twin Peaks.
Also, while it's purely a personal thing, I really can't stand the Ada character. The whole shadowy, puppet master double agent in heels character is both really tired and insultingly convenient at every turn. Even in more subdued characterization, she felt out of place in the original RE2 and here they amped her up shamelessly. To me, Ada embodies all the worst impulses of the RE series beyond the first games, and generally the more heavily she's featured in something, the less I like it.
Finally - and I know this is more a visual flourish than anything related to narrative - but is there ANYTHING more brutally dated than martial arts bullet time sequences? A lot of people say the early 00's have no discernible culture, but if one existed it'd almost have to be some manifestation of black-clad people backflipping at quarter-speed whilst bullets and daggers fly perilously close to their heads and necks.
All that being said, I actually enjoyed the game more than I did when it first came out - likely because I had really low expectations and no longer have the unrealistically lofty expectations for anything bearing the Resident Evil name that I probably had when this game was released. In terms of what it tries to be, the game is definitely fun and plays exceptionally well for something so old and ambitious. There are also a lot of really cleverly designed stages and sequences. As a piece of level crafting and player engagement, it's a pretty great game.
But it definitely takes all the things I loved most about the story - characterizations, narrative tone, themes, relative believability - completely in the wrong direction. And, honestly, the series doesn't seem to have ever really recovered in that respect.