Many services have problem that each other and thus their valuable database is not connected to each other. imagine what would happen if websites suddenly ceased to exist due to a failure blackout - google, facebook, youtube - half of humanity would be cut off from the world. And this problem fixed P2P model.
services to replace: any file hosting
File sharing using WebRTC, ideally for IM which not supported DCC.
Cjdns is a networking protocol and reference implementation, founded on the ideology that networks should be easy to set up, protocols should scale up smoothly, and security should be ubiquitous. .
protocol to replace: HTTP
this compilated kademilia + bittorrent + git + CDN
a lot of time will pass before he accepts, however, he would solve the problem of the almost all services
Also worth mentioning: PeerTube
Protocols replace: https://alternativeto.net/software/email
email is great protocol which is de facto standard hovewer does exists experiments with p2p version.
Also worth mentioning Jami Ricochet Bit Chat Cryptocat RetroShare
P2P communications have a cons that isn't federated so not recommended every day. one exception is here https://alternativeto.net/software/riot-im/ but isn't P2P.
Problem is with non-free database. Sure, does exists project like searx which is metasearch in some engines hovewer it's just prosthesis.
Know any P2P VPNs?