Unappreciated in their time

I had a revelation the other day. Was having a discussion with a friend about some musician or artist from the middle ages and how they went unappreciated and were outcast in their time, but in retrospect are considered to be brilliant and revolutionary. I've heard this said about artists so many times it made me wonder, is it because these people are truly brilliant, or due to our contemporary arrogance. This idea that we're so much more enlightened than we used to be. Perhaps this attitude naturally leads us to praise the artists that were outcast from previous eras just for the sake of being progressive. Just a thought.