The trust model is totally different.

With a VPN you know the VPN dudes can compromise your security and you have to trust the specific guys hosting your VPN and also trust their OpSec. The failure mode is quite realistic.

With I2P, and Tor you can trust that anyone in the world can audit the code. Including the highly knowledgeable people who know this stuff.

The failure mode is very low and in reality depends on highly complex zero day vulnerabilities that can only be effectively exploited by a few nation-states, if they actually even have one.

That said, a VPN is lower hassle and probably good enough for most purposes.