I have had 3 Xiaomi phones over the years. Their proprietary bootloader-unlocker tool has always taken a good day or two of work to get the phone unlocked when I don't have adb tools /drivers installed from the get-go. Their utility gives me failures/errors/denials/"your social credit is too low" (i don't live in/near China) dozens and dozens of times before it finally decides to unlock my phone for me. I'm pretty sure my next phone won't be a Xiaomi, though it's hard to find sanely priced non-Chinese phones with good ROM coverage these days.
They're basically the only company allowing you to root a phone without loosing warranty. And it's not like other manufacturers come without FB installed as system app - yes, they're a bit worse on privacy by default, but it's not like they're the black sheep within a pile of innocents.
They respect their customer by selling hardware 50% off compared to Samsung and 80% off compared to apple. Having this with custom rom is a bargain imho.
Like which other manufacturer of the size and scale of Xiaomi? Every single one of them has locked bootloaders, Samsung even bundles ads, and all of them without fail use Google Play Services and all kinds of other proprietary nonsense that can and maybe should be categorized as spyware.
I don't know. I agree that it's not a customer friendly policy. But if your already stuck with a Xiaomi phone you have to either return it or bite the bullet, not much else you can do.
Unfortunately Google is making it much harder to run ROMs now due to the new Safety-Net bootloader checks. You'll no longer to be able to use many bank apps (or even the McDonalds app!).