I'm not sure i agree with these points.
1) We can retain Prescott's rights again with a franchise tag, so we are not back looking for a QB. And if he shines under McCarthy, a long-term deal is possible, assuring the team of having a franchise QB for years to come.
2) I don't know if we would have done any more on defense than we have done. The Cowboys still have money to spend and can create more with restructures. I think it would be a fallacy to believe we're not signing players like Griffen and Clowney because we can't. It's more likely we're not signing them because we don't want to, especially at the price they are seeking.
3) Dak has not been mediocre. He has not been a clear top-five QB (which is what he seems to want to be paid like), but he has been great at times, good at times and average at times. I'd like to see if he can take the next step under McCarthy before we dish out big money, but Dallas did not give him $31 million because he's mediocre.