why didn’t flintlock rocket launchers ever take off as a military weapon? Or a matchlock rocket launcher?

although it was impossible to create a shaped charge for an rpg in the 1800s. they could made made an exploding schrapnel rocket that can inflict airburst damage on packed formations of enemies by making one part of the rocket a motor and the other part a warhead. or they could make a carcass/thermire rocket that would spew burning fuel all over the enemy when the motor burns out and ignited the incendiary mixtures flying out of nozzles at the end of the rocket.

Thermite is a pyrotechnic composition of a metal powder (typically aluminum) and a metal oxide (such as iron oxide), which produces a highly exothermic, high-temperature reaction when ignited, creating molten metal and the corresponding metal oxide. This reaction, used in welding, metal cutting, and even some firefighting robots, generates extreme heat that can reach temperatures up to 2500°C (4532°F).