Good diction is extremely important. If the listener can't understand what is being communicated, all the technique in the world won't help.
(Facetiously, I was wondering what effect yodeling would have in voice exercises- just been listening to Jimmie Rodgers).
Alice is right, good technique is needed in all types of singing. Fischer-Dieskau singing classic German Lieder and Frank Sinatra singing "Set 'Em Up, Joe" both capture their audience with a combination of appropriate technique, good diction and sincerity in delivery.