Survivor's real problem, since probably around All-Stars, is casting. You can put boring castaways through as many twists as you want, but twists will not save a bad cast. Survivor tries to create storylines and, like any other story, good characters can save an average plot way more than a great plot can save boring characters. (And as a sidenote, Samoa doesn't even have twists so far, so there's literally NOTHING to like if you don't care about Russell.)
The editing/casting problems are very apparent now because the last two seasons have been focused solely on Russell H and Coach, but even in (what I consider are) GOOD recent seasons like Gabon, Micronesia and China, there were plenty of casting duds and people who got no screentime, such as almost ALL TEN of the fans in Micronesia.
Back in seasons like Borneo and Outback, every contestant got some screentime and maybe his or her own little storyline, even though there were a couple of UTR edits like Amber and Nick Brown (to be fair, they still got way more focus than somebody like Spencer in Tocantins). The contestants were also real people, which I think was a major factor in the success of Borneo and a reason why even casual offline Survivor fans loved some Cirie, who was a couch potato with whom normal people could relate.
Somewhere around Palau, Survivor increased the cast size and started packing boring models and actors onto the show. Now, we've had an interesting model/actor or two since this trend started (Courtney Yates is a model who was recruited by casting, I'm pretty sure), but I think it leads to bad TV more often than not and is a major reason why most later seasons only have three or four memorable contestants who are surrounded by a bunch of irrelevant chess pieces.
Of course, for the last two seasons we haven't even gotten that much. With all of the camera time going to Coach and Russell, it's basically as if the show is admitting, "Oh, crap, this cast is really boring. Quick, let's compensate by making every scene about the most deluded person out here! The audience will LOVE to hate this guy!" but, unfortunately, they're running a 0-2 average so far.
I think it's going to be very interesting to see how the editors work on Survivor 20. Are they really going to continue to ignore half of the cast when so many big characters are taking part? That would be a true disappointment and, to be honest, I wouldn't mind if Survivor DID die with the next season if they did that.
/end rant