Alena is a highly skilled tracker, using all of her senses to find the monsters that threaten the good folk of Kessig province
While you will need to activate it every turn for this to work, once you have an established board state, that's not a big ask whatsoever
She can generate a huge number of 1/1 Fungus Zombie tokens when you cast her, but then you give her to an opponent
Back in 2019, one of WotC's stated goals for Pioneer was to provide a non-rotating format where Standard cards would rotate into by 2019, Modern's card pool had become so large that it no longer served the needed role of format where you can use your Standard cards after rotation. Pioneer was designed as that retiring home of sorts, where Standard cards could see play after being rotated out
Since coming out, however, its proven itself as a deadly deck strategy when paired with the formidable Dusknoir evolution line
The bigger errata came with Shimmering Skies, when Bucky, Squirrel Squeak Tutor received an errata to increase its cost, remove ward, and require you to shift Floodborns into play to trigger it, to reduce its prevalence in Discard decks