In a free society, secrets do not stay hidden for long. They are gradually revealed.
I was underwhelmed by this episode.
I was amazed by how strong these two ships were, considering how quickly Starfleet ships went down in the past. How long did it take for the Kelvin universe Enterprise to fall victim to the swam ships? How long did it take for the Melbourne to become disabled after losing nearly half of her saucer to a Borg attack?
Who said the Federation is a "free" society? There's a whole lot of terrifying technology around that is capable of destroying whole worlds. Based on every single series secrets in the federation do stay hidden, and often for a very long time. As for how tough they are, that depends on the tech of what they are up against. Here we see Starfleet vessels vs. Starfleet vessels which they are designed to last against not the freaking Borg which are much more advanced as an example.