I feel like the movie had a lot of complicated stuff to deal with and throwing in some hints that Nora's killer was a supervillain might be kind of confusing and too much for the general audience. It's not like Barry himself ever had any idea that there was anything unusual about the murder in the comics until Thawne told him. Also, while they might have considered doing Reverse Flash in a sequel, this movie definitely seems to work with the same premise of the animated film where it is just a random burglar.