There are so many things wrong with the two biggest social media networks, I can only scratch the surface. One would expect them to be on the cutting edge of UI, given the vast resources at their disposal. Sadly, the opposite is true. They are terrible either by design, or because they're monolithic entities mired in bureaucracy. Either way, there are substantial changes that could easily be implemented, had someone the vision and wherewithal to do so.
Both sites are plagued by random, spurious refreshes to the user's feed. Nothing is more frustrating than trying to read an article or tweet, only to have it disappear through no fault of your own. This could be fixed in other ways, but a tiny 'Lock' icon that prevents a change to the timeline or feed would give the end user a modicum of control, while still allowing the proprietors to otherwise force updates.
One feature Facebook could stand to take from Twitter would be the ability to create a new post without forcing the user to scroll back up to the top of the interface. Facebook's borrowing of hashtags from Twitter is a complete failure, given that the tags have a limited lifespan of about a month. This severely limits their usefulness, and has handicapped usage from the start.
Likewise, Facebook's notifications icon is quite crippled, maxing out at a hundred notifications. This makes managing a large account impossible. A quick and easy fix would be to group 'Likes', 'Comments', and 'Shares' into separate subdivisions, and eliminating the arbitrary restraint.
The way the sites utilize bandwidth at times strikes me as wildly inefficient. Users are often forced to download an image, and then re-upload it, even though it exists on the respective site's servers already. This strikes me as harmful to both users and the parent companies.
Facebook did finally allow people to share non-sharable images without referencing the originating account...but only on mobile. This is otherwise a valuable feature.
Simply setting focus properly can improve efficiency and the user experience. Two glaring examples on Facebook involve sharing. When sharing to groups, the focus is not set to the groups line, requiring an additional click. Likewise, when an item is shared, the share box remains in focus, preventing the user from scrolling down via the keyboard. Both are annoying occurrences that could be easily remedied in a single day.
Twitter fails massively when it comes to user account suspensions, where accounts are suddenly placed in limbo without cause being provided, or any indication as to when the account will be usable again, if at all.
Facebook will decide a new word is verboten, ban a user for thirty days, and when they come back, dig deeper into their history to ban them again...for the same word. 'Tranny' is the latest word deleted from the Facebook lexicon.
Most of all, despite the block and unfollow options, both sites still rely heavily on centralized censorship. To say nothing of their arbitrary targeting of various sub-cultures. Shadowbanning, account suppression, and outright deletions are a huge failure that will lead to end users migrating to other, more open platforms.
At the end of the day, though, these are major media propaganda wings, not simply social media sites. It's nice to think they could care about the user experience, but the reality is they are more about social engineering and reinforcing certain belief systems than providing a forum for sharing ideas.
Steemit, thus far, strikes me as the best newcomer to the field, with its lack of ads or ideological censorship. What site is your favorite challenger to the reign of Facebook and Twitter, and why? What features would you like to see either site add?