Champion was a new mechanic that cared about a specific creature type, allowing you to turn a creature of that type into a bigger, more powerful creature
When one shuts down a new one takes its place
If you want to draft Rabbits, you can
One way to make this guy work would be to change the creature types of creatures in play with something like Unnatural Selection and then remove them from your graveyard with something like Tormod's Crypt
It is true that there arent an overwhelming number of Blue, Black, and Colorless dragons, but at this point there are more than enough to support a Silumgar Commander deck
For most people during Odyssey, Balance was still seen infrequently, and a lot of comparisons were drawn between the two