But UEFI is more sane. Bios systems map the first 512 bytes which are both code and partition table into ram. Into that you need to cram enough code to locate stage 2, which I think tended to be located in the alignment space between the MBR and the next sector. Stage 2 once loaded needed enough logic to find and load your boot partition, and load your config from it, parse the kernel list and finally load one of those kernels. I seem to remember grub hard coding where the stage2 actually was, although I might be wrong about that. Either way it was a kinda fragile mess.
Sure, every boot process needs to get enough logic loaded to do the next thing, but with efi this is all taken care of during efis various internal loading phases, nicely located in code on onboard flash where it probably should be. By the time it comes to look for what you want to load, you are already in long mode and we aren't hiding stuff in places not covered by a partition definition. It is kinda annoying they didn't consider a boot filesystem with large enough file storage for big images (exfat, udfs, other reasonable choice, we have the filesystems) but we can cope with that.
The process for detecting bootable partitions and updating boot entries is a lot, lot saner than BIOS systems tend to be. Sure there are details of the design I don't like, and I kinda agree with your points there too, but substitute those for better choices and you still have a reasonable overall framework.