I wouldn't say it flies under the radar, it's pretty widely acclaimed, but I also know a lot of people who consider it hard to stomach/too depressing to finish so I think it ends up being more niche than you'd think it was. I actually liked season 1, but it's definitely not the strongest and it tonally may as well be a different show.
Personally I feel it's one of the best dramas to exist, even divorced from the "it's a cartoon about talking animals, but it's actually serious I swear!" thing. I haven't been as genuinely invested in a show since it ended, though I'm probably not going to watch it again for a LONG time (that last season took a lot out of me when it came out, it's too much man).
That said I still watch the Christmas episode every year ("A tree? INSIDE the house? Now I've seen everything!")