I'd say 80/20. 20% being the casuals fault. Casuals are the majority for any community period. They are the life force. But nerfs or changes are not directly their fault. Because casual players don't care enough or are not invested in a product enough to complain constantly in a constructive way on the forums. They however do back the vocal minority. If a few hardcore fans are vocal enough across the Internet the casual base who also have this issue propel the minority into direct attention of developers. So in a way yes. Casuals are apart of any problem. However games can't live without them. And the minority can't make any headway without them. I could go into about how modern games are more casual to drive more sales. But I don't feel like writing that much.