One of the fundamentals of singing is to understand the very real importance of diction!
Diction is how we can be understood when singing a text, whether it be an Opera aria or a Pop song. Diction is not the starting place, neither is it a cure for serious vocal issues, for its existence is dependent upon other factors being present first.
Diction can be a helpful aid in the process of re-education and repair of vocal muscle function. For instance, the repetition of a “ne ya, ne ya, ne ya” might be good to encourage movement in the mouth and mouth pharynx that sets up a more free and conducive environment wherein the vocal muscles are more likely to be able to function properly.
With that being said, an attempt at good diction can only do so much. If the registration and vowel formation is seriously in error, then full realization of good diction is completely impossible.
Remember, all of the voice is interconnected. When there is a problem in one area, then all areas will be negatively affected. How much more so when there is a problem at the sound source, for it ripples outwards!
Yet, if the registration and the vowel formation is correct and concomitant to one another, then the “chew food” mouth is free to chew up all the yummy consonants with the vowelled tone flowing over the pitch steps. Thus, we can sing text. Our listeners will be able to understand what the song is about, and that is always a good thing.