Tor Browser is Tor's killer app. I2P needs a secure simplified fingerprint-free browser that only does basic HTML, otherwise you're just asking for trouble.
Is there anything Tor related built into that browser?
Couldn't I2P users also just use the Tor Browser and get the same benefits of less fingerprintability?
Normal browsers being used is a massive downside for anonymity of I2P. The Tor browser tries to make everyone on the Tor network look the same.