There are numerous examples of ontological reduction, or elimination in the case of moral anti realism, the denial of the existence of a philosophical God (Russell's brute fact) and physicalism/materialism. A lot of these theories are generally accepted as being the most accurate today.
However, a lot of the power of these arguments comes from the fact that they are attempting to prove the existence of very little. If they had to prove the existence of something, then they would have far less power. As I will demonstrate, arguing for a lack of existence is far easier than arguing for an existence, but this shouldn't affect an argument's overall power.
Consider this thought experiment. Conceive of a sentient, thinking entity that has no experience of the world and trying to persuade them that trees exist. This would likely be impossible. Now conceive of trying to persuade them that trees do not exist. Whilst trees do exist, it is easier to persuade the entity that they do not. So, facility with which we can prove something should not equate to whether one theory is better than another.
Take the case of emotivism. It is very easy to persuade us the moral properties do not exist, as we have little intuitive means of experiencing their existence. This shouldn't mean however, that moral anti-realist theories succeed over realist theories, simply because it is easier to argue for.
It is because of this that I believe that the reason for the general acceptance of these theories is that they are easy to believe and argue for, not that they are necessarily correct. Therefore, I ask the question, shouldn't these ontologically reductive theories be re-evaluated?