Using a downloadable theme on your product is somewhat akin to using Wordpress to program your web app. The compromises will be dictated by the CMS/Theme, instead of you being able to call the shots
Say you need a tool to reorder categories. You know the best way to do this would be with drag and drop, but the theme only has table views! So you place an "order" field in a table view and hope for the best.
Then you realize that having a line chart for displaying open cases in a bug tracker is stupid, but it's the only view you have so you stick with it.
All these little compromises form an incredibly expensive form of technical debt, and pretty soon you have a product that users wouldn't touch with a stick. It's better to have an ugly product that works well than a pretty product that's a pain to use.
Say you need a tool to reorder categories. You know the best way to do this would be with drag and drop, but the theme only has table views! So you place an "order" field in a table view and hope for the best.
Then you realize that having a line chart for displaying open cases in a bug tracker is stupid, but it's the only view you have so you stick with it.
All these little compromises form an incredibly expensive form of technical debt, and pretty soon you have a product that users wouldn't touch with a stick. It's better to have an ugly product that works well than a pretty product that's a pain to use.