The 1961 film, which you referenced in your headline, was a feature film- I saw it on a Saturday matinee when I was a kid.

https://www.imdb.com/title/tt0055207/

It was a whimper, not a bang, usually considered one of the worst of the form. Rock-bottom budget, tired, hackneyed, formulaic story, poor acting, and much of the running time filled in with stock footage. Released to theaters eight years into television's entertainment dominance, it was a sad ending to the genre.

now the shift again is to streaming . have a grand day.

It might be interesting to have a look at some of the better ones.

A locally-owned movie theater in Tacoma used to offer old, vintage Golden Age of Hollywood films, and would preface them with cartoons, newsreels, and a serial chapter, just like the old days. Saw a few of them there when I was a kid; the old Flash Gordon serials. Cheesy but fun.

They don't do that anymore. The theater I mentioned still exists, but now offers first-run films.

I watched some Captain Marvel episodes yesterday and I see that they also have Terry & The Pirates, Flash Gordon, Green Hornet, etc..