A lot of these suggestions have already been made, but I want to reiterate some of them:
- A Resteem Tab - This should go without saying, and it's been mentioned several times already. This would greatly reduce clutter on a user's page while making it easier to navigate for users looking to follow a particular other user and see their content, as opposed to resteemed content.
- UI Improvements - Adding night mode was definitely a step in the right direction, but as @drakos pointed out, the UI is still sparse. It's bare. Steemit has to spend some time developing a user interface that grabs a potential user's attention and marks it as unique. This doesn't have to be ostentatious or clogged with features, but it has to be more discerning than what we currently have.
- A Native Messenger - We've been relying on steemit.chat since I joined in August and before then, but forcing users off of the page to interact socially is not conducive to keeping users on the platform and using it. Most activity is either between steemit.chat and Discord, but it would be absolutely fantastic to have an onboard messaging system that allows you to DM individual users without having to search them out in a Discord server or chat room.
- Change Voting Reward Allocation - As @ats-david said, linear voting has been an abject failure and has caused more problems than it's solved. I'm not thrilled about n2 voting, either, but surely there's something else that can be implemented to address this issue.
Scammers slightly butchering the spelling of recognised steemians over in steemit.chat would be really inconvenienced by this.
(Can you imagine how bad the man-in-the-middle attacks would be if we did the same thing for transactions as we do for pm's?)