alt Hacker NewsThis isn't effective because Little Snitch only sees the domains so apps can just serve the trackers on the same domain as essential services making blocking impossible.
The only way to prevent malicious apps from affecting your privacy is to not install them or not give them network access.
I derive lots of value from Little Snitch on my Mac, so this approach is more effective than not having anything.
And yes, having the ability to deny any app network access on iOS would be great.