Why is the debounce cool down not working?

You're trying to set the the callback for rmtevent.OnServerEvent on the client (a localscript).

When the tool is Activated, you need to call RemoteEvent:FireServer() with what arguments are necessary.

You'll have to split your code between the server and client, like so:

A LocalScript (in the tool)

local remoteevent = game:GetService("ReplicatedStorage"):WaitForChild("Plotting");
local player = game.Players.LocalPlayer;
local tool = script.Parent;

tool.Activated:connect(function()
    if(not enabled)then
        return;
    else
        enabled = false;
        remoteevent:FireServer(tool.Handle.Value.Value);
        wait(0.8);
        enabled = true;
    end
end)

tool.Equipped:connect(function()
    print("Equipped");
end

A Script in ServerScriptService

local remoteevent = game:GetService("ReplicatedStorage"):WaitForChild("Plotting");

remoteevent.OnServerEvent:connect(function(player, value)
    local strength = math.random(1, value);
    player.leaderstats.Strength.Value = player.leaderstats.Strength.Value + strength;
end)

Sometimes it doesn't work if you wait until end. Try doing a simple print so it sees it as it's actually waiting for something

local rmtevent = game:GetService('ReplicatedStorage'):WaitForChild('Plotting')
local player = game.Players.LocalPlayer
local Tool = script.Parent;
enabled = true


function onActivated()
    if not enabled  then
        return
    end
enabled = false
rmtevent.OnServerEvent:Connect(function(plr)             
local value = math.random(1,script.Parent.Handle.Value.Value) 
player.leaderstats.Strength.Value = player.leaderstats.Strength.Value + value 

    wait(.8)
print("Done")

end)


    enabled = true
end


function onEquipped()
print("Equipped")
end
script.Parent.Activated:connect(onActivated)
script.Parent.Equipped:connect(onEquipped)