I think you're being too harsh on him. We don't know how his 'Seeing' works, but he sees the future. It's very likely incredibly traumatic for him, and it's not like he has a guide - only Lift has a Spren who knows much about what's up at the start. As for why Renarin isn't so forefront in fandom, I think as someone else mentioned, it's because he's not a primary character right now. His brave and/or interesting actions are done as a part of another character's plotline, and they outshine him, so it's easy to miss. Avoiding the shipping stuff, as I find that stuff silly.
As for Szeth, I'm really not looking forward to the next book. I agree with Kaladin, he's a simple coward hiding behind the 'rules'. He could change, and Brandon has the talent to do so, but I still find him the _least_ interesting character in the series. And as this series includes Elkohar, that's saying something.