The old saying goes, 'the clothes don't make the man', to which I reply, 'Yes that may be true, but they certainly don't hurt.'
For instance, take this blog. For the past few months I've used one theme that - while not ugly - wasn't the best looking theme in the world. The readability of the text could have been better, the page elements were too close to each other, and (despite originally desiring) there was far too much white space.
When I chose to that theme my process for making my decision was to look for all the features that I wanted. That list remains largely unchanged: the theme must be clean and minimalistic while making it easy to read the content - be it text or visual.
The main problem of looking for a theme in this way is that most themes seemed to fit my requirements. I found it very easy to convince myself that most themes I found fit my requirements. This process wasn't efficient and caused me to deliberate much more than necessary.
This time I focused on everything the theme could not have. I focused on all the cons a theme could have, all the things that I could absolutely not live with, and narrowed my search from there.
This approach turned out to be much more efficient. It's easier to know what I don't like when I see it rather than hypothesize my ideal theme and match concrete examples against my image of perfection.
I focused on the concrete rather than the hypothetical, allowing myself to focus on what I was seeing and forget about what I was imagining. A large problem with trying to match an idea of perfection is that an idea is too fluid: it can shift and change before its even fully defined.
Through process of elimination I was able to narrow my choices and make the best decision possible. I found this method of elimination rather than inclusion to be much easier to find the appropriate theme for my uses. There's a lot of choices available but only one turned out to be the right choice for me.