If IPFS is BitTorrent + git, and ActivityPub is Distributed Messaging + Linked Data, then p2p-ld is IPFS + ActivityPub. We build on IPFS and are heavily inspired by its design and shortcomings revealed by practical use.
No identity misses the social nature of infrastructure. Where bittorrent had trackers, there is no similar concept in IPFS to organize archives.
Hence the need for filecoin, an exogenous incentive to store, but then it becomes transactional which generates its own problems.
Trust! eg. its use in phishing attacks is because there is no way to know who the hell a given CID is owned by. It needs to be possible to do social curation, or at leats know when something is riskier or not.
Lack of metadata means having to build a lot of shit post-hoc, like IPLD and multihashes and codecs and whatnot.
Not permanent storage! Identities retain custody and control over objects in the network.