You don't need to put down Vocaloid to support UTAU. If you would rather see more UTAU original songs in the world, support those who already create them, perhaps even contribute to their projects with your own skills, or even write songs of your own. Perhaps reach out to those who currently write Vocaloid songs and encourage them to pick up UTAU as well.
But I digress, so here's an example to contribute to the original question- I wish that all of Police Piccadilly's Cevio and Vocaloid songs were also sung by Yamine Renri. Her voice and the way she's tuned by the producer are absolutely beautiful, and when a Cevio or a Vocaloid gets used instead, it feels like something was lost.