I tried watching SFU but I just gave up mid way into the second season I find basically every character to be unlikable. I also find Nate, Claire, Brenda/Billy and their parents, Parker, and Gabe are all taken to such an extreme that is just makes the whole show unrelatable and frustrating to watch.
Interesting. I can understand your point of view, though it cuts the other way for me.
Six Feet Under approaches its main characters as deeply flawed individuals, makes no apologies about it, and as such, it takes longer to feel attached to them and understand them. I don't think you have to like them or find them relatable, per-say, to appreciate that their flaws are intrinsic to who they are as human beings. The first couple seasons are a slow burn and the development of these characters doesn't happen over the course of a few episodes or even a season though.
Ruth's overbearing self-righteousness, Claire's naivety and obnoxiousness as a teenager trying to find herself, Nate; always searching, never content to compromise and live with what life has given to him, Billy's bipolar disorder... by the end of the series, as a viewer, it feels like you know the Fisher family -- their personalities and imperfections growing on you as much as the characters have grown themselves. There's not one singular moment you can point to when they evolved because it's a gradual transformation that is paced astonishingly well. There's no doubt that their imperfections are taken to the extreme from time to time, though I mostly found this to be the case with the Chenowith family. The show does delve into their dysfunctional history later on which explains the eccentricities of those characters.
The reason why SFU resonates deeply and is in my opinion, as genuinely human and relatable as a drama gets, is because it's brutally real in its depiction of human nature and doesn't sugarcoat anything. Its basic premise is an introspective exploration of human mortality and an unflinching portrayal of everything life and death entails. I've never had a show take me through the gamut of emotions, from the highest highs to the lowest lows, it did. SFU has its bumps along the way, becomes cliched sometimes and has a few cringe-worthy developmental moments in its middle seasons like any other show but just like its flawed characters, it makes the show more endearing. If you ever do re-visit the series, the series finale, considered one of the greatest series finales ever conceived, is transcendent...