Although Scorcese has an enviable track record, his 2016 film Silence fared very poorly at the box office. Since 1990, it had been a passion project of Scorcese's, but he went through considerable difficulty getting it financed, as his earlier box office bomb Hugo had already scared off formerly-reliable investors.
After the failure of Silence, Scorcese made a deal to distribute his next few films with Netflix, which seems like the right move for him. To me, it feels like the audience for a strong adult drama would rather stream the film in their homes than venture out to the cineplex. Certainly I would not have paid $14 for the privilege of seeing Silence on the big screen, but I had no problem watching it on Netflix.
I'm not too interested in defending the merits of super hero films against Scorcese's argument because his argument is simply inflammatory trolling, not worthy of a counter-argument. It reminds me too much of another one of my film heroes, Roger Ebert, who in his latter years tried to claim video games were not art; thankfully, after a lengthy online series of arguments, he did that thing which people rarely do on the internet: admit he was wrong to present his opinion as though it were a fact.
My personal favourite project of Scorcese's is actually a documentary he made in 1995: A Personal Journey with Martin Scorcese Through American Movies. At the time I watched that film, I was actively looking for recommendations on great movies I should watch, and ultimately compiled a list of hundreds of movies which I then proceeded to see as I was able to (eventually I watched them all). A Personal Journey... features Scorcese talking about the history of cinema and introduces clips from a variety of unusual, somewhat-obscure films which Scorcese enjoyed. I wound up watching most of the films he presented; I didn't care for all of them, but there are many which I wouldn't have heard of if not for him. The single most valuable recommendation I received was for Kevin Brownlow's documentary Hollywood (and that documentary led me to seek out various other films).
And that's why I'm disappointed with Scorcese's ignorant remarks about super hero films. He has an open heart for films from his youth which fell under the radar, but he is intellectually uncurious about the films today's youth enjoy, yet feels compelled to share his uninformed opinion anyway. Certainly not all of the recent super hero films have been successes (just this year both Hellboy and Dark Phoenix bombed at the box office), but no one gets to decide whether a film is 'art' or not. One can express their opinion, but beware the elitist who wants to self-servingly define art to their own validation. How can the director of a piece of pulp novel trash like Shutter Island take umbrage with the dazzling creativity of Taika Waititi's Thor: Ragnarok? I don't mind hearing Scorcese's opinions on film as a fellow lover of cinema, but I have no time for people seeking to (ahem) silence their competition.
Above all else, I reject dichotomous thinking. When anyone - elitist snob or rabble-rouser - tries to insist there are only two options (ie, "cinema" and "not cinema"), don't believe them.