I have a colossal scroll of captains but I like it. It means I never need to spend coins or gems in the Tavern.
To me, the problem isnt the quantity so much as the pointlessness of the single commodity captains. Apart from the XP Captain I've never used, there isn't anything these single item captains can do that we can't accomplish with the three basic ones - Drew, Universe, and Sailor. IMO the best thing they can do with Lumbert, et al, is change then from "% higher profit" to "% higher cargo capacity" . That way they could be useful for both collecting cargo and delivering it. It would make them more valuable than Universe because of this flexibility and potentially more valuable than Drew because of the % multiplier rather than fixed number of units.