Solarius will be able to give a better answer, but this is my take.
X-Com Files per the description is still in Alpha, so very unfinished. However Solarius's development philosophy is to work on this in "arcs" within the broad story. So when he releases a new arc, it is very solid and may introduce new enemies, missions, etc. The result is that you get an extremely playable work in progress. The early game is very well fleshed out, and I believe you can play to completion, though the late game may be just a vanilla experience.