I think part of the reason we like R2R so much is because that was our introduction to the band. It's hard to describe what made it so revolutionary for us. It wasn't just one thing, like the vocals or the groovy riffs. I think it was because, despite the fact that this vocalist was screaming all the time and the music was heavy, it came across as so fun and energetic. At the time, we were listening to stuff like Static-X and Korn and Slipknot, which was all about aggression and, in many cases, raw angst. We had no idea that screaming vocals and heavy riffs could be fun (Drifter, Egonomic, System, etc). For us, it redefined what metal could be. It's possible we could have had the same revelation if Clayman was the first album we'd heard instead, but I think R2R was uniquely positioned to help people like myself (whose only experience with metal was nu metal) cross over to this kind of music.
And I think the album is just very well-balanced. Anders delivers just the right amount of cleans and never really outside his range; there are still great guitar solos and leads throughout the album; the electronics elevate the atmosphere without being overbearing or crowding out the guitars; the lyrics are genuinely interesting (this is subjective, of course); and the album grooves like nothing else. I understand the feeling that the album was a dumbing-down of their sound, but, looking back, I felt it was them striking a perfect balance between their Colony/Clayman sound and something completely new.
We listened to STYE, which had just been released, right after, and we were big fans of that one as well. But it seemed to be going for a particular style and wasn't as balanced as Reroute was. And, personally-speaking, I thought it had some misfires.
By the time we branched out and listened to their previous material, our thoughts were "wow, this is different, but also good." It never really occurred to us that their old stuff was better or worse than Reroute. But I think that's where my opinion that TJR and Colony were their pre-Reroute peaks solidified. Whoracle and Clayman are good, but imo they're a bit uneven, each having a handful of tracks that I find just kind of okay or meh, or just missing something that their immediate predecessor lacked.
And yeah, I completely missed the controversy during 2002-2005, lol. My first contact with another In Flames fan, outside of my brother, was after Come Clarity released.