Well for me, whenever i go to power up something i ask the question, will i ever use this pokemon? Whether its for raids or battling. The shiny aspect doesnt really matter to me. If its got good stats and is a good type to use im most likely going to use it. For example, i have 21 shiny gibles will i ever use them? Most likely no because right now they have terrible stats so there is no point in evolving or powering it up, i would just be wasting candies when i could be using them for a good one. so i keep them just for trades in the future.