I'm not really sure what the point of these sorts of article is - do they want to let feral cats roam free throughout Australia unrestricted? Do they want feral cats to be taken into captivity?
It's not really constructive to try and argue that Dingoes and Tasmanian Devils are excluding cats from the food chain. Dingoes are absent from much of southern Australia - and so they aren't competing with cats in the first place. Devils are stricken by a disease epidemic and are more scavengers than hunters - they aren't outcompeting cats. Native marsupials that cats might be competing with would probably more or less include quolls - and guess what? Quolls don't seem to be able to outcompete cats.
Then when it comes to cat numbers, the argument seems to be that unless we're certain about numbers no feral cat culling is worthwhile. That's a strange argument, given that the link to the ABC's Fact Check on cat numbers seems to conclude that numbers are estimated at anything from 5 to 20+ million but aren't verifiable. While we can't verify numbers (nobody has the time to conduct a survey of every cat in Australia, like we do for humans), I think it's fair to conclude feral cats outnumber domestic cats at least 2 to 1.
Thinking too much about the ethics of conservation is as dangerous as not thinking about it enough - humans caused the cat problem, so we should fix it. And also fix the cane toad problem, the fox problem, etc.