I was very disappointed that Floyd Gottfriedson's Mickey Mouse newspaper strip continuation long stories stopped being printed in Walt Disney's Comics and Stories near the end of the 1940s, because I didn't keep the newspaper pages, and wanted to have those stories in the more permanent comic books. And I was unhappy that the continued printing of his later stories, during the early 1950s were re-drawn by lesser artists. I was further disappointed as the early 1950s progressed, when the Gottfriedson stories were stopped altogether, and Paul Murry took over drawing "Walt Disney's Comics and Stories" ' Mickey Mouse serialised long adventure stories. I was frustrated in 1950, when Carl Barks was taken off the Donald Duck 10-page lead stories in "Walt Disney's Comics and Stories", to work on special other books. I was again heavily disappointed when Carl Barks retired in 1966, and the last long Uncle Scrooge adventure story he wrote and storyboarded was drawn by an artist whose work was very inferior to that of Barks.
I was disgusted at the end of 1962, when Whitman/Western Publishing ended their printing/distribution deal with Dell Comics, and they printed their comic books under their own imprint, "Gold Key Comics". which had much more advertising, and so, less comics pages, and poorer quality paper, and the colouring became atrocious, with panels coloured randomly (as far from realistic/natural as possible). And the bulk of the artwork and story quality seemed to be produced by people who didn't care about the quality of the product. The same things happened to the quality of the Dutch Donald Duck Weekly and related comic books at that time. At least there was a "revival" of Disney comics in The Netherlands, starting in the early 1970s, and lasting through the 1990s, when fans from the 1950s (who really cared about making a good product) took over the editorship and production. I'm proud to say that I worked on stories during much of that period.
During the 1980s we had a Mickey Mouse book ("Micky Maandblad"(Monthly)) which printed Floyd Gottfredson's long adventure stories, from the 1930s through early 1950s for the first time in Dutch comic books, and in full colour. I was very disappointed in 1987, when they abruptly stopped publishing that series, before having finished re-printing Gottfriedson's stories (never printing about 20% of them, - none of which were printed in US comic books, to that time, and only finally printed in a black and white collection a few years ago).
A similar disappointment came in 1989, when the Dutch collection of Carl Barks' Disney Comics work "Alle Klassieke Donald Duck Verhalen" (black and white only), came to an abrupt end due to lack of enough buyers, short of finishing all of Barks' stories.
I didn't have any US comic book series stop being printed during my collecting period, but I stopped collecting ALL of the series' I collected, because the original good artists, and the early good writers' work stopped, and the later stories and artwork wasn't worth collecting, or even reading. I quit reading "Super Duck" around 1956, when original artist, Al Fagaly started cutting way down on his number of stories, and most of the stories were then drawn by other, very inferior artists, and the story writing was also much weaker. I was also disappointed that Walt Kelly's Pogo Comic books came to an abrupt stop in 1954, so he could concentrate fully on his newspaper strip (their runs had overlapped for 2 years).
I WOULD have been bitter that some of my favourite series just stopped abruptly during the early to mid 1950s when comic books in USA/Canada were under fire for being non-educational and a corrupting influence on children, IF I had known these books existed, containing the great artwork from Ben Sangor's comic story shop, staffed with moonlighting or ex-animators. I would have been a big fan of, and collected Creston/ACG's "Giggle", "Ha Ha", and "Funny Films", as well as Nedor/Standard's "Barnyard/"Dizzy Duck", "Coo Coo", "Goofy", and "Happy" Comics. And I would have been very disappointed that they just stopped abruptly (my favourite Standard series in 1953, and ACG in 1955).