Respectably, no tool - be it I2P's garlic routing, Tor's onion routing or anything else - could ever provide "complete untraceable anonymity"; that is a huge (and potentially very harmful) misunderstanding of what these techniques can do, I strongly encourage you to learn more about them to correct that misconception.

Both projects have designs which have inspired each other and have relative advantages and disadvantages. Technically, I like I2P, but I accept I may be somewhat biased there. Practically speaking, Tor has a much larger anonymity set because it is far more widely used and receives more support, with very well-established volunteer outproxies. I would never criticise anyone for contributing to either: Tor in particular has the widest practical impact of any tool in this space.

This distributed random idea is a very impressive achievement; I'm glad to see it work in the wild! Congratulations.

I'm not sure what you mean about "stigma". Any reasonably effective solution in such a politically-charged space as the anonymity and privacy of human communication is likely to become controversial to some degree.