I will agree it's about 30% less code on average, but whether it's "team friendly" or "debug friendly" is quite another matter. Debates over such often rage for months.

If it's truly superior, then form a company called Functional Magic or the like and out-compete OOP rivals and eat their lunch. Proof will then be in the pudding, no more talk. (Some co's have tried similar without long-term success, at least outside of niches, as it does well in finance.)

If FP is say 15% more productive, such a company would eventually just outcompete OOers by growing 15% a year. Even 5% a year would catch up in roughly a decade. If you truly believe in FP's superiority, do it! Unleash the FP Kraken! When you are golfing with Warren Buffett & Gates, you can say, "I toldja so, fore!..."