Battlecruisers made sense within a narrow technological window

With hindsight, was developing battlecruisers worthwhile?

Yes to a degree in their original period, but their useful technological window lasted only a couple of decades.

The answer avoids judging the concept solely through hindsight. Battlecruisers addressed a real design opportunity when machinery power, weight, and hull size allowed a new combination of speed and heavy armament. Their value depended on missions that rewarded catching weaker cruisers and avoiding stronger battleships. Advances in machinery and battleship speed rapidly narrowed the interval in which that tradeoff remained uniquely useful to only a couple of decades.