The UI is functional and easy to understand. It'd be nice if people who had complaints would actually voice the problems they face with examples and maybe even solutions. You know, instead of just sounding like a whiny child who can't just say they're struggling with minor changes.

It's all part of the the step plan:

1. identify the problem

2. Think up a solution

3. Implement the solution

It gets an extra half step or two in groups.

1.5 Ask others for their input on the problem

2.5 Have a vote/poll to get the most liked solution

I’m pretty sure an instance can have custom UI and there are mobile apps that look different too. But I remember being a Digg user 15 or so years ago and the main reason I didn’t switch to Reddit was that I hated the UI. Eventually I did switch as Digg started to die, but the UI really grew on me and I would much rather use that old Reddit UI than the new one.

My point is, I think they don’t like it because they’re just not used to it