I agree it's the format. Adventures are long-form stories and strips are short-form delivery. They only worked in the past because the public was conditioned to that delivery. Once comic books, radio, cheap novels, and tv came along, people didn't have to overcome the hurdles of such short installments. The adventure-as-strip was obsolete.
As much as I love Star Wars and as much as I love Al Williamson's art, I could not keep up with or follow the Star Wars newspaper strip. They were later reprinted in Amazing Heroes about 12 or so at a time. That was easier to read, but still had to deal with the awkward scripting of first panels. The run didn't really become a 'regular' story until Dark Horse put them together and removed the repetition and smoothed out the transitions.