Unlike Tor, which is built around accessing the clearnet anonymously, I2P is primarily designed around keeping traffic in the darknet. When you join I2P, you route traffic for other nodes but only within the I2P network, it will never leave through your clearnet address.
The equivalent of Tor’s exit nodes are called “outproxies”, but they aren’t often used, there aren’t very many of them, and you have to specifically set them up manually as it isn’t the default behavior like it is for Tor.