Fediverse

One button to expand pictures similar to RES would be a big improvement

Built-in keyword filters are another one

And of course, multi-communities

A UI can be measured in a bunch of different ways, most of which should be measured and balanced against each other.

I recommend this video essay, where a UX professional (formerly at Microsoft) took over the UX for the FOSS music composing app Musescore and shares a lot of the lessons learned along the way: https://youtu.be/Qct6LKbneKQ

a user friendly user interface is one that the user is already familiar with. It is subjective, determined by the user, and will vary from user to user.

Think about the placement of face buttons for an xbox controller vs a ninttendo switch controller, specifically A and B. The function of menu accept is always on a, and menu back is always on b, but the physical placement of those buttons are opposite on the competing platform. Now think about a playstation controller, and where it puts menu accept and menu back. The glyphs are different, but a nintendo player will find it intuitive while the xbox player will be confused.

Juat copy what is most used so people dont have to learn anything new ever again