What does having a better UI have to do with a search engine rendering results that are what users expect and trust? Why should a site with a better UI outrank a brand? I don't even see the correlation there.
To begin with, if by "better UI" you mean "better conversion", how would you expect Google or any search engine for that matter to reliably determine the conversion rates of all (or at least the vast majority) of the web sites on the internet? Not everyone uses Google Analytics (though many do). But would you still be using it if you knew Google were using your analytics data to rank your site? If that ever becomes public, I predict a mass exodus from GA.
Secondly, higher conversion rates don't necessarily mean a better customer experience. Conversion rates are misleading. Sites with high conversion rates could have a terrible overall customer experience. The "customer experience" with a company doesn't end at the end of a purchase funnel on your web site. Google can't track whether products are shipped on time, arrive in good condition, are billed correctly, are easily returned when there is a problem, etc. These are all the things that attract users to brands... and the things that make unknow web sites/companies a much less attractive option in most cases.
You have to remember... Search engines are built to help people navigate the web. A large percentage of the time people already know which company/companies or site(s) they are trying to find, and they are simply searching for the keyword phrase(s) that will raise those URLs to page one so that they can click on the link (perhaps they can't remember the company name or their URL). In fact, I would say that is the case more times than not.
People simply trust brands far more than they do some Joe running a web site out of their basement. Perhaps "Joe's" web site looks better, has a better conversion funnel, maybe even sells a better product, but people like what they know and are familiar with and that is brands.
If the job of a search engine like Google is to help people find what they are looking for then it makes sense that brand sites and sites seen as authoritative would typically outrank less authoritative non-brand sites even though they might actually have a better UI.
I don't see this as Google trying to "keep a brotha down"... They are simply trying to give users what they are looking for. Users don't search for sites with the best conversion or UI. They are looking for sites for companies/brands that they already use and/or are familiar with so that there is some level of "trust".
If you want to compete... spend your time and money establishing yourself as a brand. Don't rely on SEO. Market your company using as many channels as possible. Differentiate yourself like Zappos did through customer service... And eventually you might just find yourself a brand like Zappos did.