Here's a few things GNUnet replaces and why it's better:
Bittorrent is replaced by GNUnet "filesharing", it's trackerless, it provides a search function, users can adjust their level of anonymity for publishing, downloading, and searching.
DNS is replaced by "GNS", it covers the "decentralized" and "secure" points in Zooko's triangle, it a pet name system.
VPN is replaced by GNUnet VPN, which is just VPN over GNUnet so it can take advantage of the p2p network.
TCP/UDP/SPDY/QUIC is replaced by "cadet", takes advantage of the p2p network.
There's also a DHT.
And there's lots of other stuff that's in-progress.
Bittorrent is replaced by GNUnet "filesharing", it's trackerless, it provides a search function, users can adjust their level of anonymity for publishing, downloading, and searching.
DNS is replaced by "GNS", it covers the "decentralized" and "secure" points in Zooko's triangle, it a pet name system.
VPN is replaced by GNUnet VPN, which is just VPN over GNUnet so it can take advantage of the p2p network.
TCP/UDP/SPDY/QUIC is replaced by "cadet", takes advantage of the p2p network.
There's also a DHT.
And there's lots of other stuff that's in-progress.