Oh my goodness.
Birds... flying... is also "completely unnatural?"
Wow. That's... special.
I'm not sure I know how to talk to you, but I'll give it one more go.
Cats are not a native species anywhere. They are a domesticated species. We have been domesticating them for thousands of years but their native ecosystem is... nowhere. Their natural prey is... nothing. We feed them because they are a domesticated species, bred by us, for domestication.
If domesticated cats go outside unsupervised, they are an unnatural component to an already evolved and developed ecosystem that has a natural balance and has taken a very long time, millions of years, to get there.
And alongside that, all living things, animals and plants, have evolved in order to fit into these naturally balanced ecosystems. So throwing ANY unnatural and non-native predator into the mix is going to cause serious disruption. Even more so if this is a predator that is being professionally cared for by vets, fed as much food as it needs by humans, and cared for in a warm and safe home that it doesn't need to fight for or build itself. It's going to have a hugely unfair advantage over other large predators at the top of the food chain so that carefully balanced ecosystem is going to be seriously threatened.
This is not the same as birds having wings, it's not the same as foxes having claws and sharp teeth, it's not the same as hedgehogs having spikes. Those are biological traits that have evolved over a very long time that the ecosystem has managed to fit into the balance of things.
All parts of developed ecosystems and food webs are connected, and inter-balanced, as I am sure you learnt in primary school.
For example, if a local fox population is decreased or wiped out, this will likely increase the number of their natural prey, such as rabbits, which will likely have an impact on the local vegetation which rabbits eat.
If a bird or bat population is decreased or wiped out, this means there will be less predators to keep insects in check and also less seed distributors (because birds distribute seeds), which again will have an impact on vegetation, which might effect animals which eat the vegetation such as rabbits, and if there are less of those then there's less food for the animals at the top of the food chain and so on and so forth.. it is all connected. You've seen the lion king, right? We are all connected in the great circle of life, Simba. Even Disney gets it.
So, quite frankly, claiming "animals are animals, none is more important that an other" is definitely bonkers batshit crazy at best, and shockingly ignorant and short-sighted at worst.
If we just chose what animals we wanted everywhere all the time, the world would be a very different place. And not in a good way.
Hope that helps.