I think a large part of the modern view of the Medieval times being ‘backward’ come from two main sources: 1-propoganda that came during/immediately after the various Crusades/Iberian Reconquista (not to mention the subsequent discovery of the Americas);

Close, but not quite there. The modern image of the Middle Ages mostly does com from propaganda of the Enlightenment period when intellectuals, artists, the upper classes etc wanted to distinguish themselves from what was before, and then some from later periods pushing some things back in time (witch burnings were not a medieval thing and the peak of plate armour was in the 16th century).

I know a german youtuber working on improving our image of the Middle Ages to a more realistic one, if you deal well with automatic subtitles I can recommend Geschichtsfenster.