You mention exit-node sniffers. Well of course exit nodes are limited, but still it is the volume of traffic which passes through that creates a layer of anonymity. Of course if you are signed into an account, or have all of your extensions activated you can get identified. The TOR network works with circuits, and routes in a way that has a high level of anonymity, specifically when you're on a .onion address. If you were interested in darknet you wouldn't be using an exit node, because the darknet is literally everything before the exit. It's true exit nodes can be setup by anyone, but the traffic is still not easily traced. The issues is the internal network can and has had vulnerabilities that allow users to be narrowed down by the path they take, I'm pretty sure they try and improve as they can, can't cite specific issues. I'm trying to be nice here cause it's steemit, but I'm a bit skeptical a person of the darknet would make this claim. (if you're wondering no, I'm just into security, you can check an older post I made on tor). I agree i2p is very interesting but has less traction.