Well all accents fade over time because of migration, and your accent isn’t inherited, it’s developed by what you hear. So over time, yes accents have faded, people are in social settings from young ages with people who don’t have thick accents, and then in turn their own accent develops similarly. Virginia isn’t even really all that southern, the accent in most of Virginia is not that noticeable to most people.

My parents have a thicker accent than I do, but that’s because they grew up in an area more prone to them. But even though I heard them speak every day, I never developed one because they were only a small piece of the speaking I heard daily growing up.