What's the difference between Diction and Pronunciation?
Nowadays people tend to conceive the diction as what it is not.
The diction only defines the right or wrong way to read, act or sing something specific. It is not to be understood as a synonym for Pronunciation or Phonation. The diction always has to do with communicating one's emotions in front of an audience, in the choice of words to use, without having anything to say about pronunciation.
We could pay attention to the subtle difference between vocabulary and dictionary. Both have written forms, so both have pronunciation implications, even if the most modern ones use the phonetic alphabet. Vocabulary is a collection of words with their meanings, while the dictionary is a collection of words with their meanings and some famous sentences or sayings that show their use.
Once this concept is understood, it will be evident to everyone that the clarity of the pronunciation is fundamental. In fact, to express one's emotion to others, one must give the right energy and intention to the words, without distorting their comprehensibility. Looking at the whole thing, to be comprehensible it is not enough to pronounce every single word of a speech correctly, but it is necessary to manage and preserve all the existing pauses.
A phonation or diction error is always linked to poor muscular coordination of the various parties involved: there is a big difference between pronouncing a word clearly and thinking you have done so!
In reality, phonation and diction are made by unconscious processes, automatic, outside the conscious control of our brain. For a person to regain possession of it, it is necessary to make a clear path of training, completely ignored by most of the voice professionals.
For example, the tongue plays the main role in the articulation of words and almost all modern bad professional teachings tend to limit its mobility in really absurd positions. It is obvious to anyone that limiting the mobility of the tongue will only produce people who speak or sing with very unclear and comprehensible pronunciations.