You're missing the OP's point, which (not to put words in the OP's mouth) is:
1 - A design does not exist in a vacuum. It is there to do something (in this case, sell shoes). It is impossible to separate good design from its contextual purpose - and in this case he is suggesting that you are (apparently) unqualified to fairly judge Zappos' design, not being from a sales background and all. Assuming you don't have sales experience, I would be inclined to agree.
2 - Zappos' purpose is to make money selling shoes. Would your UI push more sales? If so, then there's cause to look at your design. If your UI will decrease sales, then why in the flipping world would anyone consider your design? There is also no such thing as "no difference" - all UI changes, however minor, impact conversion and sales.
Personally I object to the presumptuous and condescending tone that this redesign is done in - you're assuming that Zappos is staffed by a team of idiots who couldn't care less about clean web UI. I don't work for Zappos, but given their success (and their site) I highly doubt this is the case. Making something web-2.0 does not automatically make it better.
I also happen to agree with OP that the testimonials are annoying and interrupt flow - customers are here to look at the store's offerings, not hear testimonials. Put it somewhere less intrusive. If I walk into a restaurant, I'd expect to hear about the menu - not what their ratings is on Yelp. The testimonial is also so often abused by nefarious ne'er-do-goods that its mere presence raises suspicion in users.
Your search box also removes functionality by completely tossing out search parameters - which IMHO demonstrates your lack of consideration for the specifics business requirements of the company (something many UX people do but will never own up to). The "search by" feature I would gather is very important to shoe buyers.
This post is already getting long, but I need to hit another point: you started your entire post with a very confrontational "why is your website a confusing mess"?
And then you fail to make any meaningful changes to the UI. The tab-based navigation is identical save for some padding and sizing changes. The product selection columns are identical. The search box is identical save for your decision to remove search features. The general layout is identical, in fact, save for your decision to add in the testimonials - how does this reduce confusion, exactly?
If you're going to make loud, bold-letter claims about the confusion inherent in a design, at least make the effort to change the design, as opposed to give it a slick font-and-button-texture makeover?