Obviously there are a number of technical differences between THE holocaust and other genocides. The main being it happened in a Western country so we can’t ignore white people are capable of genocide too (since we generally conveniently forget the North American aboriginal purges). I’m not sure that is a good reason to single it out- it maintains the distinction between a “civilized” genocide and “barbarian” genocide. We should focus more on the pure humanity of the problem.
Firstly I agree that holocaust memorials aren’t trying to “hog” the limelight. I wonder how various Jewish groups/people would feel about a concerted movement to morph the tradition into an “All genocide” memorial day.