Hello.
Bonnie was on cheap kibble when she came home at 8 weeks and I moved her straight onto raw with no problems. She still inhaled her food (thank goodness for kongs), but it suited her very well. I use chicken or meat for training, and we have Millies too.
When we brought Bon home we already had two cats and a geriatric Border Terrier called Rosie with lymphoma. As part of caring for Rosie (she lasted six years after diagnosis) I became very interested in the quality of their food and found that the closer I could get it to what they would have eaten wild the better. Dogs and cats have no need for wheat or cereals and found research pointing to a relationship between the tenacity of the cancer and the level of carbs in dog food. That sealed it for me. I know everyone has their own views and circumstances. For me, the diet made the difference to wee Rosie's longevity and quality of life. My cats haven't needed a vet since, and Bon only goes for annual check up (apart from the bee sting....). Clean teeth, not smelly, smaller poo, shiny coat, and loads of energy (sorry, that's just cockers!).
And bizarrely, my little cat is a complete pain in the bottom if she gets her mitts on Whiskas or anything. To the extent we call it 'Cat Crack' as she behaves so badly on it.