As someone who has spent their professional life writing Objective-C (first pre-ARC, then ARC), now mostly Swift, the biggest benefit of Swift over Obj-C is how

As someone who has spent their professional life writing Objective-C (first pre-ARC, then ARC), now mostly Swift, the biggest benefit of Swift over Obj-C is how much more difficult/explicit it is to write unsafe code. You can totally shoot yourself in the foot with Objective-C. Swift is much safer. That in itself has undoubtedly led to an industry-wide improvement in code. Not to mention, obviously, that async/await in Swift is a huge leap forward, especially from the ever-rightward-moving blocks-within-blocks in Objective-C. If you don't see how you're "sacrificing safety by continuing to write Objective-C", then you are missing something, IMO.