We should keep in mind that xat may want to preserve its overall user interface, whether it's the chat or the new web. I'm sure they could've created a Discord 2.0, but that wouldn't be xat anymore, would it?
While the new web looks like it doesn't bring many changes, it actually does and I'm not sure why new features wouldn't matter. I'm quite excited about them.
So let's take a look, what actually seems to be different?
We now see groups which are currently promoted. I think that's pretty cool for people who often promote their groups.
There's a quick access to featured, popular, supported groups, as well as groups with games.
We now have a linking to the xat facebook page.
It's more obvious what options you have for the group you're at (embed, inapp, maybe more in future?).
There's now a login button, a logout button.
There's account information (perhaps we'd see more information in future, such as if your account is held).
It appears we'll be able to edit Settings soon, which is a good step in the right direction to get rid of the macros-mentality.
The bottom navigation is more dynamic, I like the fact that it doesn't reload the page anymore, when you switch tabs.
Overall the design is more elegant and modern. I think Admins did a pretty good job, and I think it makes sense to introduce this now, as xat is slowly getting rid of flash, switching over to HTML5 entirely soon.