The Bug:

The bane of arthropods enchantment no longer inflicts slowness when applied to ranged weapons or projectiles.

In 1.20.6, the bane of arthropods enchantment on bows inflicted the slowness effect on the said mob that is shot, but this is no longer the case in 1.21. 

Steps to Reproduce:

1. Summon a spider and give yourself a bow enchanted with bane of arthropods by using the command provided below.

   /give @s minecraft:bow[minecraft:enchantments={levels:{"minecraft:bane_of_arthropods":5}}]

2. Shoot the spider using the bow without fully charging it.
3. Observe if the spider emits slowness particles.

Observed Behavior:

The bane of arthropods enchantment no longer inflicts slowness.

Expected Behavior:

The bane of arthropods would inflict slowness.