First off, not everyone is using I2P to hide their torrenting. If they were, I'm pretty sure we'd have to worry about a well-funded actor (like the RIAA of old) flooding the network with new nodes to be able to expose users.

It's instructive to read the I2P threat model, https://geti2p.net/en/docs/how/threat-model, as it details a number of potential attacks within reach of a large corporate or state-level adversary