The Bug:

Firefly bushes cannot be replaced by trees or mushrooms.

This is because firefly bushes aren't part of the "#minecraft:replaceable_by_trees" and "#minecraft:replaceable_by_mushrooms" tags.

Steps to Reproduce:

1. Place down a firefly bush and open the F3 debug menu.
2. Observe if the bush has the "#minecraft:replaceable_by_trees" and "#minecraft:replaceable_by_mushrooms" tags.

Observed Behavior:

Firefly bushes cannot be replaced by trees or mushrooms.

Expected Behavior:

Firefly bushes would be able to be replaced by trees or mushrooms.