Goranger and Kamen rider 1 weren't quality and quantity in one package?
That is very different. You have to remember, Toei's shows are lower-budgeted than Tsuburaya's, and that was an advantage. Plus, the SPFX are minimal. The emphasis of the shows was more on action than SPFX. Both
Masked Rider and
Goranger are
great shows, among my favorites, but they sort of do have a milked-out feel. That's not exactly a bad thing, though.
Tsuburaya Productions, on the other hand, tends to want to do more new things. They're not Toei. Toei is a major corporation, not unlike Toho, that only does superheroes on the side. Tsuburaya is a purely SPFX studio that does all sorts of experiments. The Ultra Series isn't the only thing they do, even though it's their most famous creation. And back when the "Big Three" were produced in the 60s, Tsuburaya pushed the envelope for SPFX, and those shows were
not cheap. But they wanted to end said shows out of respect for them, rather than milk them out. If they wanted to make longer shows, that's their decision, but sometimes you feel as though you've done all you could, so you end the show gracefully, leaving behind a memorable body of work. And Tsuburaya moves onto the next new thing.
Like I said, different strokes for different folks...