Every release macOS got more closed and removing features I cared about. At the same time introducing stuff that only works if you're all-in on Apple. I use every OS under the sun. So that didn't work for me. Because all Apple's cloud stuff works on Apple alone (with a handful of exceptions on windows).
The lock-in of passkeys was just one of the things that bothered me. Not really the attestation per se, I'm aware it doesn't currently have it though I wouldn't be surprised if they introduce it if passkeys actually take off.
But like I said, Apple does have hardware control over other features. They do have a secure element which is just like a TPM which blocks you from changing certain files on the system and if you disable system integrity protection they turn off some of the features of the OS, like the ability to use iOS apps on macOS. It's basically DRM.
This really embodies what's wrong with the world in 2024 — people believing in their world views so strongly that they ignore actual real world evidence that is directly contrary to their very strongly held but incorrect world view.