Steemit will not have the polish of Reddit; the same competitive advantages of the blockchain model (efficiency, distribution of rewards) mean that less resources are available for this purpose.
Why are less ressources available to have the polish of reddit? Sorry but your sentence doesn't make sense to me.
But Steemit doesn't have to beat reddit as a social platform, or in UX... it only has to be "good enough" so that the combination of social features and the incentive mechanism outcompete the UX of Reddit alone
Why aim for good enough when you can aim for the best? Thinking that the reward incentive will make up for the shitty UI is wrong. If it was true steemit would have millions of users right now but because of the crappy UI and lack of social feature the site doesn't retain new users. I am also convinced that the killer app on the steem blockchain will not display rewards on the interface, it will be a back end thing only. If youtubers had earnings displayed publicly on every videos do you think it would attract more people to create videos? It would not, it will just increase the perception that youtuber are just here to make money which is a negative in a social media site where natural interaction is everything.