Not taken "seriously" by whom? (Sorry if somebody's already answered this.)

Certain now-antiquated coots like myself thought "Lock the Door, Lariston" was fantastic in 1966.

Likewise the Clancy Bros. & Tommy Makem, now mere squares and curiosities to many, but once cutting edge to the few.

Neither group was made up of instrumental geniuses (though Makem's whistling was pretty darned good), and that may be part of the reason for later being out of favor.

Both were a little outclassed by the more versatile Dubliners and (how I hate to say it!) Irish Rovers.