Uh, I know I could Google the answer, but I think it's more fun to ask here

! I'm asking to better understand the references in this anime: what was the goal of Shocker? A generic criminal organization? Did they want world domination? By what means?
Oh, world domination, definitely. Shocker was the ur-evil organization of Showa-era
Kamen Rider. They were based on the Nazis in certain ways -- the pursuit of world domination and the creation of a master race, their emblem and iconography, their stiff-armed salute.
Their primary method was to brainwash abducted humans and transform them surgically into cyborg kaijin (monster-men) who would carry out various episodic evil plots designed to undermine society or kill or transform everyone or whatever the writer of the week came up with. The kaijin generally had special powers that they used to carry out their plans, and destroying them would conveniently undo whatever harm their powers had inflicted on their victims, the environment, whatever. Your pretty standard Showa-era tokusatsu premise.
If you've seen
Shin, you know the basic story, that Shocker abducted Takeshi Hongo and modified him to become Kamen Rider, but he was helped to escape before they could lobotomize him and reprogram him as one of their agents. (They should've brainwashed him first. Poor planning.) It's traditional that the majority of Kamen Riders share the same origin as their enemies, or at least a related one. It was kind of a dark premise, in that the monsters Kamen Rider killed were actually brainwashed human victims of Shocker, but the premise was that they were too far gone, their humanity and personality already destroyed by the brain surgery, so if anything he was just putting them out of their misery.
Shocker Combatmen (
sento-in), the interchangeable grunts, wore skeleton-themed costumes and luchador masks and cried a high-pitched "ee-ee!," which seems silly at first, but when there are dozens of them doing it at once, it's actually kind of chilling and menacing, like something out of Hitchcock's
The Birds. (Actually the early Combatmen had berets and face paint, and the luchador ones were the personal guard of a specific villain, but then they took over, I guess because it saved on makeup time, or just because the producers or audience preferred them.)
In my
Tangent Knights audio drama trilogy for GraphicAudio, I approached the overall premise as a pastiche of Heisei-and Reiwa-era
Kamen Rider and other tokusatsu, but the Eclipse organization I introduced in Book 2 was an homage to Shocker and other Showa-era evil organizations.