In that case: An unmanned kamikaze ship still needs the mass and size of a capital ship, it needs sublight engines and a hyperdrive and it needs an advanced piloting system. It has to stay with the main fleet in case it’s needed, so it costs additional money to operate. Why not buy a regular ship for the same price, which is much more versatile and not limited to one single use? And don’t tell me “it’s just a joke”.
I’m pretty sure a small TIE Fighter could do some damage to the Rebel cruiser.
In Rogue One, we see that the smaller rebel ships didn’t do much damage to the Stardestroyer, when they crashed in hyperspace, so no.