I'd like to elaborate on my earlier comments.
I still say the UI is really, really off in this game. Minecraft had a fairly nice UI before even indev. But this game, I don't know.
What's with this overlap?
The number of things wrong with this picture (my modified faithful texture pack) is insane. Bad scaling, overlapping hearts, hearts not aligned in any sensible way, and the fact had to remove the sections in between the blocks because they're not far enough apart.
Or how about the weird UI stretching it does?

vs
The fact that texture packs do not edit the font, the buttons, or the item backgrounds is kind of frustrating as well.
Also as a former Minecraft server owner, the multiplayer drives me insane. There is no player list. There are no colors in chat. There is no scrolling in chat. In fact, the chat is sort of pushed off to the side with a small font like a second-class citizen. That is so backwards, where chat in Minecraft takes a front seat to the rest of the game because it is a large and important part of every server.
Let's use a server I used to frequent as an example.

What is the very first thing you see in this picture? The chat. It is large. It is readable. It contains important information. It looks nice. Take note of the well-positioned, texturable UI elements. Take note of the clickable links and the chat colors.

This is a player list. When you press [TAB] you can see who is online, some useful information for talking to people on the server with the aforementioned chat.

This is a popular Minetest server. There is no player list. The chat is small and hard to read. It contains no important information for the most part, that is all in the MOTD box which is also small and hard to read. There are no colors or formatting. There are no clickable links. The UI elements are, in fact, looking slightly nicer thanks to a mod, but the main problems still remain.
I can't even begin to set up the server the way I would a Minecraft server without multiple worlds, customizable and large colored chat (actually important), block logging and rollback plugins, and a good selection of other plugins. Of course, some of that comes with the maturity of the game and community.
I really hate to shit all over this game. I love the idea, I love the moddability. I have nothing against the devs of this game, in fact I am amazed that someone is in fact able to make a game this cool open source. That said, I'm fucking done with Minecraft after this Microsoft and EULA bullshit and it crushes me to see that the closest replacement isn't making any faster progress than it was before. You'd think I'm not the only one that's leaving that camp, but maybe not.
I think what this game really needs is an art guy. Some better textures, better lightmaps, music, and overall better UI would make the game infinitely more enjoyable.
Sorry for the long-winded rant post. I didn't mean to come off as an asshole, I just wanted to point some things out that I would totally fix myself I knew how to code well.