That kind of logic cuts both ways: "If you don't want a device with a locked boot loader, just don't buy a device with a locked bootloader".
Unfortunately, as consumers, we're trapped between a rock and a hard place. On the one hand, I would want 100% freedom to use my device exactly as I see fit and run any software I want, without any form of curation from the manufacturer. On the other hand, there are plenty of software companies who do shitty things when given absolute freedom over what to do in a user's device (tracking / spying / etc) and I welcome buying a device where the manufacturer helps me fight some of that.
So I can absolutely see both arguments. And I think both types can coexist. I am happy my iPhone doesn't allow Meta to say "to use WhatsApp, you must install the MetaStore®, give it root and install it from there". I would not be happy with those restrictions on my desktop.
You fix that by making root access inconvenient enough that companies can't rely on the average random user having it enabled.
For example force you to wipe the device to unlock it as another person said in another comment. Or make it so that if you don't unlock it within 7 days of the device purchase and first boot, you cannot unlock it anymore.
Granted they require you to opt-in in order for the photos app to be usable & if you go out of your way to avoid opting in they make your photo-browsing life miserable with prompts & notifications. But you do still have to opt-in.
If you dare turn off Play Protect for example, you will be asked to turn it on every time you install or update anything. Never mind that you said no the last thousand times it asked.