For most websites, I typically develop custom themes. I work with a designer who comes up with the look and feel which I then implement. I like to start with the underscores or _S theme theme as it provides a skeleton theme that adheres to WordPress standards. My approach is that when working for a specific client, the theme should provide the implementation for that website, not an all-propose solution.
However, sometime circumstances require I take on projects where the approach is different. I am currently working on a project using the Flatby theme from Mojo themes which was selected by the project manager. The theme has an incredible number of options and has a responsive layout. There are many animation and parallax settings which allow the WordPress themer to implement a myriad of designs. What could be wrong with this?
In order to use this theme and come anywhere close to the demo, you must have at least some understanding of HTML and CSS. I think many people when purchasing themes like this do not realize the skill level required to actually make them work!
So, what is my conclusion? I think that the WordPress community would be far better served with simpler themes that are easier to implement and that generate cleaner code. After all, not everyone needs or can afford a custom design for their website.