Strixhaven is released on MTG Arena tomorrow, and these are the cards being swapped in initially. Sadly, the Mystical Archives didn't add any new uncommons since the uncommons are all cards that are currently in standard.

Some of these swaps are to take out lesser played cards (Such as Sunset Pyramid or Wilt) and adding in some more playable new cards.

Some of these swaps are using the new cards as minor tweaks or upgrades (Such as turning Moment of Craving into Lash of Malice) to provide better options and also to try out new cards.

And one of these swaps does nothing :) (Erratic Visionary -> Soothsayer Adept).