Yeah, I recall that pic of the Spc Ops and the Afghans chasing Taliban while on horseback.
And, there are some places you just cannot take even a tank.
A British Revolutionary War general said that "Anywhere a goat can go, a man can go, and anywhere a man can go, artillery can go."
I'd hate to see someone try that these days with the several thousand pound howitzers.
Even the light towed system I served on, the M119A1, weighs in at 4000 pounds.
But with horses...
It sounds like something General Wolfe would have said when insisting that his forces could ascend the cliffs to the Plains of Abraham above Quebec during the French-and-Indian War.
Don't forget the Brits made some significant use of Congreves Rockets, and these were considered to be artillery. I don't see a traditional field piece, with limber, being as mobile as a light infantryman.