You do not need previously released cards to play cards from this set
We've seen two Secrets of Strixhaven cards with the ability so far: Arcane Omens and Archaic's Agony - both five mana Sorceries, both incredibly garbage
You don't need to be built around her with legends or pestilence effects for her to be a very solid option, just having a merfolk looter that prevents you from early attacks by being a 1/3 would legitimately be enough, but then you also get a late game threat and some extra free looting when you cast your commander
Sword & Shield was the first set released in the SWSH series on February 2020, concluding with Crown Zenith on 20th January 2023
Perhaps if it cost five to cast and five to active it would have been fair, but at three to tutor (Tinker) and zero to activate, it was completely abusive
We just have to be careful not to deck ourselves with Chasm Skulker