You seem to be implying that Debian makes large significant changes to upstream software for the sake of integration with the rest of the OS and that Arch makes none at all. Neither of these is true.
Also if that means the program won't run at all? Or a bug that has a patch to fix it doesn't get fixed? Or a device that could be supported is instead not supported?
I've made patches to a bunch of stuff to improve kde on mobile/tablets. After short or very long time they do get merged, but meanwhile people (like me) who own a tablet can actually use the software.
