In the context that you describe the AGP "complete history," many non-enthusiasts would say the same of the Amiga. "Windows" supports AGP in version 7 and 8 and they are still being made and for sale in normal computer stores such as, NewEgg and TigerDirect. The NG Amigas are sold "hobby" quantities, and the OS support is in the hands of just a few individuals working for a small company based in Belgium.
I bought my first Amiga in 1986 ( having saved up enough after grad school) and have been an active user/consumer until the present. I have my grandparent's 1938 Philco radio that I re-wired and re-populated with vacuum tubes so it works as well. To me nothing is "complete history" as long as it is useful.
You are getting to have apples and bannas (frogs and grandmas in Serbian) mixed over here.
AGP is defacto dead, there are no new boards and cards, unlike with PCI bus (replaed by PCI-E x1 but not yet) as well as ISA bus.
Classic Amigas are dead because they are not produced since 1996 (with except of Minimig and FPGA board) and 68k OS ceased to develop with OS 3.9 (AROS 68k is backport for FPGA and Natami, Classics are kind of weak for it).
Off course, ISA, AGP cards and Classics are usable and avaliable to purchase for those who know how to use them.
USB criticism: Keyboards, mouses and other small devices don`t really need it and already had PS/2 and other standards.
Not as fast as Firewire, UW SCSI or SATA2 for data transfer (Bluetooth?) not enough power for serious devices
and mostly no plug and play as it was supposed to be.