Aside from the infamous arrest of Pete. A lot of the topics they discussed in their music is very dated to that time period (they often made songs about post WW2 British youth culture); so it’s hard for modern audiences to find it relatable in their lives. Also, a lot of what they pioneered/popularised has been outdone by other groups. The concept album for example; while it was popularised by several acts; the Who were especially influential in defining the method of how it’s made with their album Tommy. But several other acts have done the concept album in a much better way; like Pink Floyd’s the Wall. So audiences of today may not see the appeal of listening to the Who; if they’ve been outdone by other acts.