The attribute id is minecraft:player.block_break_speed. The post title is correct, but the command and screenshot are not. The command has generic.block_break_speed and not player.block_break_speed. (same for the screenshot) In short: Your command is wrong.
7410
The attribute id is minecraft:player.block_break_speed.
The post title is correct, but the command and screenshot are not.
The command has generic.block_break_speed and not player.block_break_speed. (same for the screenshot)
In short: Your command is wrong.