Anonymity isn't binary. Perfect anonymity is, and always will be, completely impossible. Practically speaking, we can only talk about reducing risk in different scenarios.

I like I2P as it has a reduced threat footprint compared to Tor as it's all internal, but it's also a smaller network, probably more vulnerable to Sybil, less audited code, etc.

Again, my point is that there is no perfect solution, it all depends on the situation and the requirements.