Thinking more on web #decluttering, I now believe that this is largely a matter of control.
My programming career started in web development and even though I was never good at the design part, it was always immensely satisfying to get my web site look just right. Perfect margins, best color scheme, nicest fonts, but all of it according to me.
Herein lies the problem: web sites are largely created to represent the tastes (or corporate style) of the creators, and not the preferences of visitors. I think that the key to a user-firendly web is giving back the control to the users.
The hard part of it is how much control should we give back. In the attachment are three versions of the same blog post: one with my current blog's theme (the green one, designed according to my tastes), one with all styles stripped off (literally zero custom CSS), and the second is the very minimal styling (mostly browser defaults, but some minimal styling to improve readability).
Which one is better for the user? I dunno.