Let me know if the issue persists. The I2P site should be near clearnet speeds. It's a 0-hop tunnel since it's using the same clearnet server for the I2P site. I don't need to additional tunnel lengths to keep the site's origin anonymous since there is a public, clearnet version already available. So your I2P traffic to the site shouldn't be routed all over the network before being able to access the site. Should be pretty direct / fast.