The pet niche is not a 100% YMYL niche. It is one of those niches that are borderline YMYL.
What exactly do I mean by borderline YMYL?
YMYL means “your money, your life”. That means Google will be extra careful while ranking content that falls into the YMYL category. Anything related to your money/finance or health/medical info will be ranked only if it comes from a credible source.
A mere SEO-optimized content in such categories cannot rank on the top of SERPs.
The pet niche can be owned by a pet owner or a qualified veterinarian. If you are a pet owner and sharing tips and products that are not related to medical advice you should be able to rank.
But if you start sharing medical informational articles about Pets then you are going to have trouble. My recommendation is to stay away from advice in your blog posts that ideally a vet should be giving.
Don't confuse Google with articles in your niche that requires a vet's approval or recommendation. Any content that a genuine pet owner can share through his or her experience will have no problem in ranking.
Google is smart enough to figure that out.
Do let me know if you have any queries.