On the subject of the Clones post prequels: I always assumed Palpatine used Clones was because they would be totally obedient (as Lama Su says) and that he could imbed them with special commands (like Order 66). With the wars agains the Separatists he orchestrated, the Clones were spread all of the Galaxy, and when he finally became Emperor, he had his entire army in place to enforce his New Order on the occupied planets.

I don't know if the Imperial army we see in the OT are just new recruits, Clones or a combination of them. I tend to think it's a combination. One reason is because we saw the Clones slowly 'transform' into the Stormtroopers we see in the OT. It's also logical to assume a lot of Clones died during the Clone Wars, which probably didn't stop during the transition from the Republic to the Empire, and the rise of the Rebellion. New recruits were needed to keep enforcing Palpatine's New Order on the Galaxy.

Maybe the use of Clones was phased out, because new Clones couldn't be manufactured because the original host (Jango Fett) died. I could think of multiple reasons. Maybe they could only make a limited number of a sample of Fett's blood before it 'decays', and maybe it's not possible to clone a clone.

Anyway, this is all reading between the lines.

I once wrote a fanfic of Episode III way before it came out, and in it was a scene where the newly founded Rebellion's first action was to destroy the Clone factories on Kamino. It had Alderaan Y-Wings, Naboo N1 fighters, Mon Calamari ships above the water, and Gungan subs underwater fighting the Aiwha's (those flying/swimming whales).