When Windows ME was released, it was little more than a reskin of Windows 98 that removed or disabled much of the 16 bit capabilities and support for the ISA architecture in favor of 32 bit and PCI. It couldn't be installed on most existing machines and was highly unstable on those that it would run on.
Windows Vista wasn't much different. It was a crappy skin and a new desktop composition paradigm requiring better underlying graphics hardware than Intel was providing at the time. Many systems couldn't upgrade to it and those that did had stability issues due to immature graphics drivers.
Windows 8 was similar, it introduced a newer kernel design that fully extracted Win32 out to userland. It also introduced Metro and other modern elements that weren't bound to IA32/IA64. It was primarily targeted at modern single screen touch enabled devices and didn't work well as an upgrade or on desktop PCs. They eventually shipped Windows 8.1 which was largely a refinement of 8 that was arguably the test bed for extending Windows 8 concepts to the desktop.