“…..They often force one to distort the syllables and meter of the text, and unnecessarily drag out the davening….”
With Carlebach niggunim?? Never experienced that, they fit nicely ; on the contrary, so many other niggunim don’t fit the text.
Hence, the oy, oy…, ey, ey,…. tra- la- la…, na-na-na- to fill the gaps.