The problem with FileCoin is that the math behind it - Proof-of-Spacetime and Proof-of-Replication - just ... doesn't exist yet. That's what the delay has been, trying to figure out how to actually turn those into usable cryptographic primitives. It's not clear that a practical, scalable implementation of the system described in the FileCoin paper is actually even possible.
(There's been some progress on getting proof-of-replication working, but it's still early stages and I haven't seen anything on proof-of-spacetime.)
(There's been some progress on getting proof-of-replication working, but it's still early stages and I haven't seen anything on proof-of-spacetime.)
Also, the economics of FileCoin don't make a lot of sense ... https://blog.dshr.org/2018/06/the-four-most-expensive-words-...