The reason I'm even here today is because my 4+ year old desktop PC attempted to install 20H2 today and the update totally screwed the boot table, then crashed to a reboot that it couldn't complete. It was only because, contrary to your assertion "that there is no longer a use for a very old build", I actually found an old Win 10 boot DVD (from 2015!) which I was able to utilise to get the MBR repaired, and the machine reverted to an operable state. During the recovery, however, BOOTREC reported that it was unable to recognize the filesystem on the Windows drive, so I figured that I'd better make a newer DVD with an updated copy of Win10, in case more complex recovery situations arise, in the future, which this SIX YEAR OLD DVD couldn't fix, whereupon I stumbled upon this asinine bit of absolute idiocy of the boot image inexcusably outgrowing the capacity of a single-layer DVD and Microsoft's ignorant 'solution' is that I buy, and create a bootable usb thumb drive (on a computer which has, again, NEVER been able to boot from usb!), then install the Windows ISO on it and set it aside someplace, potentially not to be used again for years, if ever, and they somehow think THAT is a reasonable operation?! GMAFB!
FWIW, the machine in question has USB2.0 ports onboard, and a USB3.0 PCI card, it doesn't support UEFI and has NEVER been able to create a bootable thumbdrive. Your particular experiences are FAR from universal and your criticism only highlights your latent cognitive myopia.