Though I agree with both of you, I think that there is a certain amount of success that drives these designs to continue to be made. In retrospect it's quite easy to criticize the design here and naturally, we are all pretty unanimous that it could be much better. That being said, saying "it fails because it uses textures" is very different than "it fails in it's use of textures".
Try doing a ghetto case study by asking anyone around you whom is ignorant of good design trends whether they rather login to your shot or one like this:
Did the skeuomorphic shot shot pick up votes? It won unanimously from the people I asked. As designers we can nitpick about the goals of each design and the information that had to be shown but at the end of the day, unless your designing for a community like Dribbble, it's going to be design ignorant people using your interface. The main objective of this interface should be to retain users through it and a large component to succeed in doing so is by having the form be visually compelling - not to us, to them.
Just like programmers are told to assume that every user is a malicious hacker, I believe designers should assume every user has poor taste. It's a much like how you don't see people in public wearing edgy designs off the runway despite them being created by people considered the very best fashion designers. There could easily be a company that takes these designs as is and mass produces them cheap for the public but this doesn't happen because there is a major discrepancy between designers and consumers tastes. Our job as designers is to bridge the gap in these tastes - between what we know is good and what users will actually agree is good.
Of course, don't take this to mean that I think this type of login is in any way ideal but I do think it works better than what more or less an unstyled form adhering to metro. It would be one thing if all good designers were all designing in a minimalistic style... but they aren't. The problem with the excessive paper/glass/linen/wood/gradient/etc is that good designers are using them in their designs and it forces the trend followers of the industry to feel like they somehow need to incorporate all the same elements. To me the design tells a tale of someone who believed that adding, well, added to the design. The result was something over-designed, superfluous, a cliché of what something outstanding should look like.
I think it's quite odd when people are adamantly against one style of design. I have extremely minimal designs I enjoy like the Nest thermostat and I have more skeuomorphic looking designs I enjoy like Path. To me, both are designed well because both use their respective language correctly not because they use one language over the other. Maybe some programmers can attest to a similar feeling... if you preferred Python would you rather work on a project with terribly written Python or extremely well written Ruby? The later seems obvious. One last thing to consider: if anything the reason skueomorphic design is getting hated on is largely because it's existed so long. Though a minimal design is likely harder to butcher completely, it won't be long until people are making really atrocious looking Metro apps and then all those who thought it was the be-all-end-all future of interfaces can have a beer and laugh about being wrong.
Just my opinion though. If you disagree, please don't downvote me to oblivion - tell me why you side with the camp you do as I'm always open-minded to good persuasion :)
It's incredibly annoying to see some people discount any design if it is anything more than flat and solid colors.
Everyone of all design understanding levels understands a sense of craft. Subtle gradients, shadows, textures, and effects go a long way to creating a 2d digital object of worth.
Nothing in the real world is a solid color--it has light, texture, and materiality. Stripping a visual of all of these characteristics creates an uneasy steril-ness that can feel flat and or cheap.
