Is Minfilia always useless ?

[Iscah]

While we didn't know then, we never asked if we couldn't, and we eventually did anyways.

We "eventually did anyways" through a method that we didn't know at the time, that nobody else knew at the time, and required someone else to make preparations that had not been made at that time.

Additionally it was not something we could do at will. Again, we had to be summoned. The Exarch explains this to us. We did not travel there of our own free will.

In fact we didn't even need to be summoned at all now that I think about it. You still have the option of going down to the base of the Tower on the Source and using the device to travel to the First if you ever wanted to.

And how do we use that, and what is on the other end?

The Crystal Tower didn't appear in Norvrandt until after the Flood – therefore after Minfilia was there, therefore later than the point at which you propose we use the device to warp to the tower.

Even aside of the fact that the device didn't seem to do anything until the Exarch locked onto it as a beacon, it would have taken us somewhere other than the First: either to the dark future or to the current-day Source version of the Ocular or it just might not work at all.

Though the presence of the device down in the trench has always been a bit of a question mark anyway because, assuming it was the thing that Nero's radar picked up and there isn't something else down there, it doesn't line up with the rest of the timeline. It had to be put there by the Future Ironworks if not by the Exarch himself, and if he just opened the portal to the Source and tossed it through, then it shouldn't be there until later.

(My slightly wild theory is that there was some kind of separate unmanned craft sent back separately to drop the beacon – along with a curious message in a bottle that we found on the beach one Rising...)

So no, it is within our power to travel any rift at any time as long as there is a way to do so

We did not have a way to do so.

We still do not have a known way to do so outside of the specific aetherial pathways created by our summoning and then linking into the First's aethernet.

In fact, narratively (as opposed to what we can do for gameplay convenience) it seems like we don't really travel back and forth anyway, and when we do we use the Ironworks device and the mirror portal in the Ocular. We return to the Source through the mirror at the end of 5.0, and I think 5.3 as well. And IIRC it's specifically said that the Crystal Tower becomes known as the way that the Warrior of Light comes back and forth to visit.

It's also important to note that "getting into the rift" and "getting through the rift to another world" seem to be two separate things with different degrees of difficulty.

[Riastrad]

In fact, narratively (as opposed to what we can do for gameplay convenience) it seems like we don't really travel back and forth anyway, and when we do we use the Ironworks device and the mirror portal in the Ocular. We return to the Source through the mirror at the end of 5.0, and I think 5.3 as well. And IIRC it's specifically said that the Crystal Tower becomes known as the way that the Warrior of Light comes back and forth to visit.

It's also important to note that "getting into the rift" and "getting through the rift to another world" seem to be two separate things with different degrees of difficulty.

But we already know it's possible. That's the point. You are actually in the Thirteenth in the World of Darkness raid. Yes the original purpose of the Tower was to open a pathway to the Void, but Yoshida is now saying that it might just be a portal to more.

We never share information or ideas and it is becoming impossible to not address this issue.