Isshin, Two Heavens as One's ability affects only triggered abilities with conditions that are directly related to attacking, such as "whenever [this creature] attacks" or "whenever you attack with one or more creatures." It does not affect triggered abilities with other trigger conditions, such as "whenever [this creature] becomes tapped." Isshin's effect doesn't copy the triggered ability

As a brief mathematical aside (feel free to check my work, Quandrix nerds), here is a short comparison of non-generic/staple overlaps with the appropriate predecessor across each Secrets of Strixhaven Commander deck, not counting Sol Ring or Arcane Signet nor generic/staple lands: 7 cards from Silverquill Influence overlap with Silverquill Statement 10 cards in Witherbloom Pestilence to Witherbloom Witchcraft 10 cards in Prismari Artistry to Prismari Performance 5 cards in Lorehold Spirit to Lorehold Legacies 9 cards in Quandrix Unlimited to Quantum Quandrix Seeing the data laid out as such, it's hard to justify my vibes-based analysis as anything more than a poorly calibrated vibes antenna
(2009-02-01) You can choose not to find a basic land card, even if there is one in your library
Cards you choose not to cast this way (or can't cast this way) remain in exile
4 Youthful Valkyrie Uncommon - $3.05 Angel decks get another boon with Youthful Valkyrie, an exceptionally solid card that grows bigger and bigger the longer the game goes on