#wouldn't they eventually resent or abandon Janna's worship altogether when things don't change

[mollysunder]

Personally, I feel like Janna's worship in Arcane, specifically in Zaun, has faded or that she's generally unpopular as a goddess. In most League lore fir Zaun, Janna's presence is an afterthought at best if not outright nonexistent to most Zaunites. In the game, most Zaun champions react to her dismissively or with actual resentment like Renata, at best new characters like Zeri are delightedly shocked to know she exists at all.

If you think about it, Piltover has more things that acknowledge Janna with than Zaun. In League, Piltover named its wealthiest neighborhood, the Blue Wind Court, which is one of Janna's powers. Meanwhile, in Arcane, the show defines Zaun with Jinx's special birds (crows) than Janna's own sacred birds, the blue bird, in Zaun to lay claim to the space.

Sidenote: Convergence and Legends of Runeterra are the exception, but Convergence's worldbuilding is pretty opposite day on Zaun's lore and tone. And LoR's Janna and her followers don't actually fit the aesthetic of Zaun, they all look like they live somewhere else in Shurima. It all makes it seem that League really didn't know how to integrate a Janna into Zaun after the first story retcon.