I should note Google has such an attestation scheme, and there are reliable defeats for it in most situations given root access. Apps have been able to insist on hardware-backed attestation which has not been defeated for some time, but that isn't available for old devices. Almost none do so.
If this had a meaningful impact on fraud, more apps would insist on the hardware-backed option, but that's quite rare. Even Google doesn't; I used Google Pay contactless with LineageOS and root this week. I'm currently convinced it's primarily a corporate power grab; non-Google-approved Android won't be a consumer success if it doesn't run your banking app, and the copyright lobby loves anything that helps DRM.
You could also imagine having them integrated directly into the phone, but with a physically separated button or fingerprint reader to authenticate. The TAN generator could even have the ability to override the display to replicate the UX of authenticator apps.
The web app has been running with this security model for decades on PCs, and it has been fine. The whole narrative about remote attestation being necessary to protect users is an evil lie in my opinion, but it is an effective lie which has convinced even knowledgeable IT professionals that taking away device ownership from users is somehow justified.
The bank’s bad processes are not an end device fault.
I'm alright with limiting liability for an unlocked/customized phone (for things that happen from that phone) - but that's a legal/contractual thing. For that to work, it's enough for a judge to understand that the phone was customized at that time - it doesn't require the app to know.