Cooldown on script not working as intended?

whenever you have a function in :Connect, it will always run apart from other code, your task.wait(8) won't affect rest of the code. what you want to do is called debounce, you will create a variable and whenever you press ClickDetector, you will set it to true, then after 8 seconds you will set it back to false, and the code will only create the plate if the variable is false.

local CreatePlateDebounce = false

function CreatePlate(Position)
    local Plate = Instance.new("Part")
    Plate.Position = Position
    Plate.Size = Vector3.new(4, 0.25, 4)
    Plate.Color = Color3.new(0.944961, 0.94493, 0.944945)
    Plate.Parent = workspace
end

script.Parent.ClickDetector.MouseClick:Connect(function()
    -- not CreatePlateDebounce is same as CreatePlateDebounce == false in this case
    if not CreatePlateDebounce then
        CreatePlateDebounce = true
        CreatePlate(Vector3.new(50, 0, 50))

        task.wait(8)
        CreatePlateDebounce = false
    end
end)

now to demonstrate that :Connect does not affect rest of the code you can put a while true do loop in it:

script.Parent.ClickDetector.MouseClick:Connect(function()
    while true do
        task.wait(0.1)
        print("Hello, World!")
    end
end)

after clicking more and more times you will notice your output get more and more flooded by Hello Worlds since all these :Connects are running together but apart from each other.