I'm always surprised when people have such a visceral reaction to anything. There's what, 20? 30? Proper big marvel movies now - are they all terrible? I literally can't believe that - yes, they are not high cinema, but there is enough variety there that surely you can't describe all of them as terrible. Unless I don't know, you just hate marvel and all their characters?
So I don't think they are at the point yet of just cranking out derivative shows and movies based on the same template.
That show didn't even feel Marvel-themed, it felt like it was just set in the same universe. The show is super gritty, dark, and realistic. Feels more like a high class thriller than a superhero show. Which it imo isn't, because the only "superpowers" I've seen in S1 are being good at fighting and a blind person having sonar-like vision thanks to enhanced sense hearing.
https://en.wikipedia.org/wiki/Legion_(TV_series)
Both very much the same template.
There is no real objective measure of a movie's quality. However by the standards we do have such as Rotten Tomatoes scores from critics, the Marvel movies all range from fine to great with the lowest RT score coming in at 66%. That means even in its worst installment two thirds of people that professionally assess the quality of movies had positive things to say about it. I don't think people appreciate how difficult that is from a quality control standpoint. For comparison almost half of all James Bond films failed to reach that 66% mark.
Someone who thinks all Marvel movies are terrible either isn't giving them a fair chance or is simply out of step with popular culture.
Now if you want to open it up to the general genre of superhero films, there are plenty of terrible movies in that group.
Maybe comic books didn't lead to delinquency
Terror of media has been an almost constant train of thought since at least the era of Plato. But most particularly it seems that Protestant Christianity is haunted by an existential terror of the imaginary.[2] At the very core of Christian teaching is the unease around Jesus' use of parables (constructs of fiction designed to reveal truth, a contradiction which has resulted in the use of much ink dedicated to the explication of how the former is not really involved at all). It could be argued to hearken back (conceptually) even to the "Tree of Knowledge", where original sin is no longer sex but knowledge itself (which would include knowledge of sex).
[1] The Novel-Reading Panic in 18th Century in England: An Outline of an Early Moral Media Panic --- https://www.semanticscholar.org/paper/The-Novel-Reading-Pani...
[2] ON DANGEROUS READING: A Warning Against The Reading of Novels, Fiction, and Other Poisonous Literature (1849) --- http://www.truecovenanter.com/against_the_world/dabney_on_da...
Catholicism has always been far more comfortable with the story and the image than its offshoots. So we can get persons like Chesterton who could posit Christianity as distinct in that it is the only religion in which God himself becomes at atheist. And Tolkien could place fiction and fact into oroborosian configurations: "Of course I do not mean that the Gospels tell what is only a fairy-story; but I do mean very strongly that they do tell a fairy-story: the greatest. Man the story-teller would have to be redeemed in a manner consonant with his nature: by a moving story. But since the author of it is the supreme Artist and the Author of Reality, this one was also made to Be, to be true."
Comparatively, between him and Lewis, it might be notable that in their major works only Lewis (the non-Catholic) needed to explicitly bring Christianity to the fore.
Popularity I don't know about. As someone who grew up in a household where Tolkien and Lewis were okay but Dungeons and Dragons was Satanic, I think for many it's more about what they assume the contents to be, rather than their actual properties. It's a spectrum. As one reviewer of a Christian horror series modeled after Goosebumps put it: "I am not sure how I feel about Christian horror books".
Such things tends to occupy that interstitial world of alternative Christian culture that recreates rock music and movies and book series, as if to have no active acknowledgement of God (or perhaps such Christian culture in general) for even the briefest moment is indistinguishable from disbelief. It is the same mindset that compels the production of textbooks that are required to invoke a Bible verse to go along with every math problem and to warn children that doing yoga will allow you to be possessed by demons (my 5th grade health book).
But, as I say, I doubt everything is haunted the same way. There are plenty of Protestants who have no problem playing D&D on a Saturday night. But, too, people aren't often consistent. There are many who would defend violent video games, but would then turn around and deploy exactly those arguments against other types of media, as if they too could somehow 'infect'.
Anything that is seen to potentially threaten the status quo is liable to upset the people who benefit from it (who also tend to hold the most power in society). Combine such concerns with overactive imaginations and a media which thrives on sensationalism and you get the perfect storm of a moral panic.
For instance, Japan experienced a similar type of moral panic (through a combination of government and media) around anime and manga at roughly the same time (or a little after) the crusades against comic books (and broader efforts against such works as Lady Chatterley's Lover) were ongoing in the U.S. and the U.K. However, in regards to Japan, the results broke in the opposite direction. Unlike in the U.S., a translation of Lady Chatterley's Lover was found to be obscene, but manga escaped, seemingly, relatively unscathed, and so it continued to develop as a medium in general and thus, now, in various incarnations, caters to a multiplicity of audiences, men and women, children to elderly, students to business professionals to housewives.
What's best and what's worst in Marvel tends to draw opinions that are all over the place, excepting that rarely does anyone rank the two Guardians movies near the bottom. Like Star Wars, I guess. You can get rankings that are wildly different, except for a few things (almost no-one is going to rank Empire very low, and almost no-one is going to rank AOTC higher than the middle, for instance).