I hate that the general conversation around !important is simply: "Important is bad. You should never use it".

Its more of a belief rather than knowledge at this point.

I'd be interested to hearing a good answer as to why one wouldn't use !important on a modifier class such as ".padding-20" or even something like ".full-width".

Surely the problem lies with your html composition if either of these classes are being used on an element that does not need them?