I understand the need to get around some of the quirks inherent in BIOS, but the idea of rich pre-OS applications just seems completely backwards. The goal for the early boot environment should be to hand off to the real operating system as soon as possible. Just let me select which disk partition to boot from and the operating system will take it from there, thanks.
> the idea of rich pre-OS applications just seems completely backwards.
is at odds with:
> let me select which disk partition to boot from
As soon as there's any UI at all, one has to deal with much of the complexity of modern UI. For one thing, I'm sure modern firmware has to support modern HID input devices, such as USB keyboards. But also, ideally, that UI should be accessible to people who can't use a minimal screen-and-keyboard UI implementation, such as blind people. This is an area where, even with UEFI, PCs fall short. I like the way Apple has resolved this on its Apple Silicon Macs [1]. As I understand it, as soon as the Mac has to display any UI at boot time, it boots into a minimal version of macOS itself, where VoiceOver and any other accessibility tool can run.
I agree, though, that in the common case where the default OS is booted, the path from power-on to OS kernel should be as short as practical. Booting into a BIOS in 8086 emulation mode hardly seems like the best way to do this. But then, a design-by-committee solution like UEFI might not be optimal either. It pains me somewhat to say this, but Apple's proprietary, vertically integrated solution might be near optimal.
its all about UX, if you have an environment that has lots of menus and settings something even bios had to control certien aspects of your system like virtualization support and such you would like to have good UX, because of that UEFI was created. Now if you wanted to do that from OS you can but you need a technology many people hate and want to remove from their systems and hardware called Management Engine. Yes this is the purpose of ME allow changing of UEFI settings from either the OS of machine itself or changing of UEFI settings from another machine without requirement of IPMI(idrac iLo and simular implementations) and rebooting to get to it.
Implementation of some sort of ME allows you to overclock your CPU from OS. So AMD has some sort of ME(of course its not called ME since that is just name of intel implementation) as well(how wide in functionality is another question) so do GPUs.
