There is so much to do or see in Sitka. It depends on what you enjoy.
It does however help things if history is to one's liking...like with me.
St Michael's Russian Orthodox Church, Sitka National Historic Park, Alaska Raptor Center, Russian Cemetery, Castle Hill( yes there's a small castle of sorts), Russian bishop's House, Shelton Jackson Museum, and the New Archangel Dancers. The dance show was "must see" in my book !
We have heard the story of Seward's folly and the US buying Alaska from Russia...well...this IS the place. Sitka was a Russian city at the time.
Sitka probably gets my vote as my favorite port of call.
This is a walking port of call and most attractions are an easy walk from the pier( tender required). Just hope for clear weather.
What worked for me was purchasing the ship's tour for the raptor center( not walking distance), the dancers which tend to sell out, and a general orientation. Then I did my OWN tour on foot.