What prevents people from obtaining or buying such devices and automating them? Using TVs as proxies is just one example of that. People will be willing to give their ID cards away too, if you pay them or beat them enough.

In fact they already do this. Buying 100 android phones and chargers is cheaper than reverse engineering whatever you're trying to automate - or was, before AI.

.. and we ban those device ids and move on. Your capital is lost.

Evidence shows otherwise. There are people making lots of money from these device farms. Right now. This isn't hypothetical.

I literally work on this. The problem is that enforcing device attestation impacts DAU so platforms don’t want to do it but it’s effective. Once the internet is unusable, device attestation will be required to access services. Ad driven businesses will start to see demand from ad buyers for non-bot traffic etc.