The thing is, this depends a lot on which side of the attack you are on! In Scandinavia, the early middle ages (called the Viking Age) was a golden age in terms of political power and influence and also a high point of art and culture.
In history there are always many sides, and often they are glossed over in the overarching narrative. For example the fall of Rome was clearly a cultural setback for Italy (which is of course why the narrative of The Renaissance originated there). But was it also a setback for the subjugates areas like France, England which now became independent?
Rome continued to prosper centered in Constantinople, but had a large setback when it was plundered by the crusaders and Venice, leading to the balance of power tipping back to the Italian states - hence the "rebirth".
Saying early middle ages was "bad" or "good" really depends on how you anchor the narrative. Same with the renaissance(s).