Only in 20w12a, not in 20w11a, attributes do nothing at all
Linked issues
Comments 3
This one, for example: /give @p minecraft:diamond_axe{AttributeModifiers:[{AttributeName:"generic.attackSpeed",Name:"generic.attackSpeed",Amount:-2,Operation:0,UUIDMost:42373,UUIDLeast:163894}]} 1
The UUID NBT format changed in 20w12a, see MC-175259.
Please provide the exact commands used.