Let's walk through the criticisms you make.
unfocused interview loops leading to poor feedback
Yes, and it sounds like that is an issue they are trying to address that.
much too long process between phone screen and receiving approval from MTV
Absolutely. I am an outlier there. I took over a year from initial interview to hire thanks to the hiring freeze. I'd like to see us A/B test different interview formats to figure out how much of the process we can remove without hurting the performance of the people we hire.
a focus on hiring those good at interviewing and not those good at engineering (hiring scores do not correlate with performance scores)
This is not so simple. There is a skill to impressing people, and everyone has trouble limiting its impact on interviews. My impression is that Google does much better than most. For instance how many times have you heard someone say that their impression was really good, but when they went through the notes the person wasn't as good as they seemed. That is a case where someone's interview skills didn't have its usual impact.
The best anyone has managed do with any hiring process is to filter out the vast majority of bad people. Successfully ranking the best is pretty much impossible. The toy model I offer at http://bentilly.blogspot.com/2010/02/what-is-intelligence.ht... is a pretty good explanation of why. Just replace TST with "interview skills", INT with "actual performance" and IQ with "hiring scores". Since both actual performance and ability to interview affect your interview results, being really selective winds up with people who are good at both, and not those whose performance is truly exceptional.
ignoring experience by offering salaries or positions significantly below candidate's current levels in the industry.
This I'll actively disagree with. Google is in a strong negotiating position. They would be amiss to their shareholders to not negotiate well. Particularly since the ability difference between "got in solidly" and "just missed the cut" is rather small. But even so, if you're good at negotiating, the salary drop is much less. And there are various kinds of incentives that make your overall compensation significantly more than just your salary.
Besides, whenever you put people into a different kind of job than they have had before, you run a real risk that they will prove not to be a good fit. A drop in compensation is only appropriate in that situation. And Google's environment is different enough that lots of people wind up in that situation. (For instance I'm an SRE. That's a Google role that you don't find elsewhere.)