Thank you so much for sharing your & yours sister's experience with the raw food diets. I will share it with my friend who is trying to get more input. I agree with you that what works for one cat may not work for another cat, whether it be raw or homemade or commercial or pork or chicken, etc.. I become concerned when I see anyone speaking in absolutes (like pork is lousy for cats) or feed raw & it will fix IBD. So much of it at this moment in time is simply opinion &/or based off individual experiences. It is frustrating for sure! I do think one vet put it best when she said they aren't really sure what is best but are working to figure it out. That is being 100% honest. It is more often than not trial & error & it is even more challenging when you are trying to do the very best for your pet, especially when there are health issues involved. Some vets--not all--will be adamently opposed to raw or homemade food while people feeding raw or holistic pet stores will talk about the prescription pet food companies controlling what vets know about nutrition. Yet, if you ask that person where exactly are they are getting their information, it is from a company selling either the raw or commercial food that carry or additives for homemade food

. So, how is this any different?! There is an argument for bias on both fronts & then the consumer is caught in it! And then to top it off, there are underlying genetics, just like with people, the inherently drive what will or won't happen sometimes. Not fair or fun, but it is the reality of it.
I want to share a link to blog posts from a vet out of Boulder, CO who is actually a holistic vet who has a cat with IBD. It was a sanity saver when I found it. She talks about trying to do everything with food & supplements & for her cat it just wasn't enough. She has to use steroids to keep her cat healthy.
She also talks about how raw does wonders for some cats, while it makes other cats worse. The more mild cases seem to respond really well to just a diet change whereas the more moderate severe cases require other medical interventions.
https://boulderholisticvet.com/inflammatory-bowel-disease-ibd-cats-part-2/
I love what you are doing

. Like you, I keep reading, try to find the science to support claims, doing some nutritional consults, getting peoples personal experiences. Ultimately, the science is not always there to direct a decision, so I make the best choice I can & try a food out. It will work or it won't work & ultimately, the cat has to want to eat it, so even if there is the "perfect" or ideal food, the cat may choose one that is not quite ideal but still works overall.
I am going to attach the link for Cummings School of Vet Medicine (Tufts U)/MA. They have a strong nutrition program & have press releases etc.. Again, just access to more information & then you personally can decide for yourself what info is helpful or not & utilize it.
https://vetnutrition.tufts.edu/petfoodology/