Listening to the example in the OP, the main problem is the trivialized oom-pah rhythm likely influenced by the West. The song itself isn't especially expressive, but mostly repetitive. Likewise there isn't much expressive quality in the singing itself. Perhaps it is a folk song with an overlay of the harder, repetitive rhythms? The male singer has a good tone. I'd describe him as a good singer. She is not bad, but doesn't have as resonant a tone, but she does get a focused vibration in the singers' palette. When reading the thread title I was expecting something far worse.

I'd enjoy hearing more examples of these same singers - perhaps in a more serious genre.