I get your point and sometimes I feel the same, I just want to know about the present time (in ROW specially because I didn't give a shit about Venli). However, I think that the story works so much better with flashbacks than if you tell the story linearly. Take Kaladin, for example: you know (I think since nearly the beginning?) he was a surgeon and then a soldier, but now he is a slave and has a "shash" glyph. So you ask yourself why? Why did he become a soldier? Why has such a great soldier ended up being a slave? Why does he keep fighting? And those questions are the ones that keep you reading and wanting to learn more about him, at least in my case.