Have you ever developed anything substantial with Objective C? If not, I suggest that 'unfamiliar' might be more apt than 'archaic'. Anyone starting a non-trivial iOS project in 2015 in Swift would still need to learn the basics of Objective C because so much of the documentation and examples were still in Objective C at that time. I don't think it's accurate to say that learning Objective C in 2015 had no benefits.