There are many interesting uses for enclaves, most of which have nothing to do with DRM. A good example is Signal’s secure value recovery mechanism: https://signal.org/blog/secure-value-recovery/
The right way to do it is the other way round: have a trusted hypervisor and run your untrusted OS in it. See TrustZone for example.
The scheme you suggest, which isn’t typically how TrustZone is used, gives zero integrity and confidentiality guarantees for applications. I don’t know if it’s “the right way” for some threat model, but for the most typical TEE use cases which are trying to establish strong integrity and confidentiality guarantees in the presence of an untrusted host, it’s absolutely not right nor useful.
Enclaves are started from host code, but host code can't see into them. In other words you have no way of telling whether the enclave you've started is what you wanted, or if it includes malware.
The scheme I've described does give integrity - after all, that's precisely how the actual trusted components work, SecureEnclave, TEE etc: you have a trusted hypervisor, and then run your secure components outside the untrusted OS, in a trusted environment in that trusted hypervisor. It gives you everything SGX could, without its fundamental design problems.
Code running in an SGX enclave is measured and absolutely known at enclave launch. The fact that enclave memory is encrypted for confidentiality is unrelated.
I don’t understand why you think trusting the hyper visor is helping anything. You are still open to this attack, and to all side channel attacks as soon as you run any untrusted code.
Research has shown that it is not a panacea, but we already knew that. It’s hardware not a full proof cryptographic solution. Some solutions have enclaves gather their results in a fault tolerant way to increase security even more.
So we could say that Intel and hardware vendors in general are looking for a solution that doesn’t exist. Or we can say that this is greatly improving your option when you are really scared of host compromises in your product.