While that's a very good use case, the desired one where you're not allowed to use the Internet unless you're using a big three approved device that can attest you're not using an ad blocker isn't so much.
There's no reason to believe this will require a TPM or depend on the presence of one. As far as I know, Widewine and similar DRM schemes successfully achieved this without any hardware assistance. Yes, bypasses exist and all the major piracy groups have them, but the objective of preventing the masses from having access to a working bypass is clearly achieved and doesn't require hardware.
The early bypass of widewine meant burning an nvidia shield (invalidating its keys) for each and every single rip.
You need something else (like Apple's FairPlay or Microsoft PlayReady) beyond that, and these definitely check your HDCP version. I believe 4k output commonly requires HDCP 2.2.
FairPlay on macOS might be based on obfuscation still (there was an interesting article on that here some days ago), but high-resolution playback on Windows definitely does involve the GPU driver somehow.
Do you have any references to back that statement up? Software-only DRMs are ultimately always either plain obfuscation or some variant of white-box cryptography, which is also anything but proven to actually work.
But in such a scenario, an attacker can also use such an attack to bypass any remote attestation/DRM/etc!
I guess you could argue that such attacks are too much work for consumers, and that low fences control big dumb animals…but I think, fundamentally, the same argument applies to consumer security functions like FDE!
Tl;dr: I think it’s hard to argue that TPMs are both useless for practical user security and a threat to free computing. It’s gotta be one or the other!