If the Bubonic plague hadn't happened and hadn't killed so many, then we might have had more thinkers and scholars to help society. Maybe the idea of art after this time would be long after. The Mongols only achievement was first chemical warfare that mainly all they're remembered, and if that is gone then they will be truly forgotten. To the Church and Feudalism they would be the same, anyone that got help from the church or their lord only survived on it besides the church and lords didn't help. So if the Bubonic plague never happened, it wouldn't be different.