I think you are confusing some things here. It seems to me that you mix up desktop environments and distributions. There are distributions like Ubuntu and Mint and about 600 others. Distributions are a compilation of packages fit together to build an OS. One part of the OS is the graphical environment, which contains usually a window manager or desktop environment. For your case let's focus on desktop environments. There are several of them, like Unity, Gnome 2 and 3, KDE 4, MATE, XFCE, LXDE, Trinity and may be some I have forgotten. Only Unity (the new Ubuntu default interface you dislike) is in some way bound to a distribution, all other desktop environments (DEs) are able to run on any distribution. Having said that, MATE is not an offshot of Mint, but Mint has a version that comes with MATE pre-installed (like other distributions, too, Salix for example). MATE is a fork of Gnome 2 (the previous Ubuntu default interface) you can just ditch Unity and install Mate on your Ubuntu instead. Or XFCE, which also resembles Gnome 2 somewhat. Or you choose a distro that comes with a DE that you like by default, there are plenty of Ubuntu derivatives that should look like you want it to be.
To give an analogy: Changing the distribution just because you don't like the default DE is like changing your computer because you don't like your monitor.
Maybe I should re write Mate to put the stuff in the right places LMAO wonder it they would get pissed !
If you feel the need to do that just do it. Nobody will blame you for it, this is open source. But it is rather overkill to rewrite a whole desktop environment (in 2008 the Gnome 2 environment contained about 13 million lines of code) just because you don't like the look of it on one distro. Would be easier to just create a theme that fits to your likings.