The documentary is compelling and riddled with contradictions, just like the band itself (said as a Clash fan). For example, while framed as the band members speaking to the truth of the tale, it also engages in the self-mythologizing the band were (in)famous for. It also can't avoid the cliched rise and fall history of so many rock bands, but it speaks to what made this band matter to themselves and to their fans.
Great documentary for people who grew up with or caught up with the Clash at some point in their lives. It won't make converts or explain how and why some called them "the greatest group in the world." Many have criticized it for the lack of full concert footage, but it's not a concert film. It is a nice reminiscence.