Precious, yes, but not too precious.
Only God is ultimately precious.
The problem you have is how can you determine that a person actually received "spiritual insight and revelation directly from the Holy Spirit"? While I think Calvin was a smart dude, I still like to check what he had to say against the scripture. You know the "trust but verify" bit.
Catholics don't have that luxury. Anything the Church says, goes. So, if the Church says the Virgin Mary *POPPED* in on three kids in a Spainish field, then you are compelled to say, "Haaaallelujah!!! Pass the taco sauce." The Catholic Church is literally littered with fake Saints that never were much of a Saint to begin with (St. Patrick or St. Francis comes to mind but there are many others) or out-and-out frauds. There is historical evidence to support this but, hey, since the Church is infallible and the Church can't be wrong then let's not mention this. Now you've added 400+ new saints to the queue to whom you can pray to who were martyred for their beliefs that people can pray to and receive divine intervention. Talk about Gnosticism. Pretty soon our Lord Jesus will be looking for a new spot.
Let's see; praying to dead people and having dead people talk to you. Not a very good theological position I would want to take.