I re-watched a lot of old Simpsons episodes recently, and I agree that there were a lot of problematic elements. But there are also a lot of strikingly insightful episodes, such as "Last Exit to Springfield," which was one of the most engaging depictions of union/labour dynamics in popular media at the time. The union workers are depicted as lazy, incompetent, disorganized, and greedy, but they're contrasted with Burns, who is explicitly shown to be downright evil.

A lot of it probably depended on who was writing a particular episode and what they could get past the producers, but there are episodes which I believe are worth defending.