In the past, most documentaries were pretty much the same: interviews with experts, a few shots from a museum, or maybe with an open book or old pictures. They were all shown as the experts were talking.
Today, the industry has evolved and documentaries are really fun to watch. They are very similar with movies. Aside from experts who are sharing their valuable knowledge, documentaries have paid actors, realistic animation and a lot of VFX and SFX. I think it can be more difficult to make a documentary than a movie because the bar is set really high these days.