I’m not so sure. Today people are fed a steady diet of CGI, often with the result of the real thing looking less real than the larger than life renderings.
Have you ever witnessed a bad car crash? Terrible to be sure, but kind of anti-climactic when compared to a good action movie. And when it comes to horror, the implied continues to have more impact than the explicit.
Again, the trick is to have them think you have done something horrific to others first. Feel free to break open the bag of tricks. 5 liters of blood sounds like a lot, but it’s really only 2 and a half big soda bottles worth. You’re gonna need a couple of gallons for full effect. The problem of course, is convincing screams.