The Marvel Cinematic Universe (or "MCU") has been in existence for over ten years, and has scored great commercial and critical success, both (as its name would suggest) in movies, and on television, both traditional and streaming. Like the comics that inspired them, the Marvel Cinematic Universe has expanded the "superhero" genre to include gritty detective noir (Daredevil), cosmic science-fiction (Thor) and geopolitical drama (Black Panther). But one genre that has not been present in the Marvel Cinematic Universe is horror.
First, a little backstory about horror in Marvel Comics. In the original Comics Code of 1954, comics were prohibited from depicting most supernatural monsters, as well as even using the word "horror". Since Marvel Comics was formed in 1961, the Golden Age of Marvel Comics had no mention of traditional horror monsters, and didn't involve its characters in horror related plots. (Although there was some mention of the supernatural in comics such as Doctor Strange, that certainly bordered on horror: I will return to that below). In the early 1970s, the comics code was loosened to present classic monsters and villains, which comics both incorporated into anthology horror titles, and into characters that were part of their "main continuity", so Marvel had stories, for example, where Dracula was fighting Spider-Man. This was somewhat of a trend in the 1970s, although by the 1980s, usage of horror monsters had become a bit passe, although Marvel comics still included elements of classic horror, as well as reintroducing characters such as Ghost Rider.
Ironically enough, some of these Marvel characters had cinematic success before the Marvel Cinematic Universe launched. Wesley Snipes starred as half-vampire vampire hunter Blade in 1998, and Nicolas Cage played Ghost Rider in 2007. But none of the Marvel Cinematic Universe movies have seemed to have taken their inspiration from Marvel's horror comics.
There be a few exceptions to that, based on how you want to define that. Because there have been works that dealt with the supernatural. Doctor Strange is a magician that basically visits hell and challenges a demon---that sounds like horror. Elements of Daredevil that deal with the supernatural certainly touch on horror themes. Cloak and Dagger is set in New Orleans and uses the supernatural and voodoo as plot devices. But, I would argue, that does not make these horror stories. The Comics Code Authority approved of Doctor Strange and his supernatural enemies while horror was still forbidden, and Doctor Strange is usually not counted as horror. And the Daredevil and Cloak and Dagger television shows are not really considered "horror", just as most comic book fans would hardly call their comic books horror.
So why the reason for the paucity of Marvel's wide horror background in the Marvel Cinematic Universe? I think there are two reasons for it.
All of the Marvel series interact, to varying degrees. A horror story set in the MCU would have to carefully establish itself as being different, setting up its own tone, mood, and atmosphere of suspense and horror--- and then, at other times, having the same character trading one-liners with Iron Man. While the MCU has established various subgenres, its basic genre is a kinetic type of superhero movie that is both humorous and optimistic, something that would in certain ways clash with a darker movie. In brief, horror would either disrupt the Marvel Universe's branding, or would be watered down by the need to fit its tone.
There is also another reason why Marvel hasn't brought any of their "classic" horror characters into the Marvel Cinematic Universe. These characters are already in the public domain, and as such, have been very well exposed. Incorporating them into the MCU really adds nothing to them. What particular draw is their to see another remake of Dracula, only with the added bonus that Captain America makes a cameo appearance? Artistically or commercially, there just doesn't seem to be an angle on "Spider-Man Versus Werewolf".
That being said, I wouldn't be surprised if the MCU doesn't continue to incorporate parts of Marvel's horror background in some of their movies, or if they produce movies and television shows that incorporate psychological suspense and horror in places, but I feel that the Marvel Cinematic Universe itself is based around a different direction, and will probably be continuing to make movie and television shows with the same feel that they have been making so far.