WindowBlinds is a very old program - consider it started on OS/2. It used to be very popular back in 90s and 2000s, but its popularity have dropped the last few years. Still, if you find any alternative Windows theme on places like DeviantArt chances are it is made for WindowBlinds. It isn't wildly popular, but it isn't unknown either.
It sounds like it really doesn't affect the whole Metro UI part of Win10, which is the part I have the biggest complaints about UI-wise.
I don't like the Windows desktop that much (I like the start menu and such, I don't like the look and feel and other things, which is why I'm a KDE fan). But I can deal with it fine; it's the Metro stuff that's really horrible to me.
