What makes you think Safari has gone stagnant? Apple, Microsoft, and Google all have different approaches to the consumer software that they put out. Microsoft

What makes you think Safari has gone stagnant? Apple, Microsoft, and Google all have different approaches to the consumer software that they put out. Microsoft values backwards-compatibility above all else, and Google values the bleeding edge and experimentation. Apple values predictability and ease of use. For example, Google created and deployed SPDY because they thought they had a better way to do HTTP. Eventually this turned into HTTP/2, but in the meantime Google is now faced with supporting both SPDY and HTTP/2, or deprecating and removing SPDY from Chrome. Apple, on the other hand, waited for the HTTP/2 standard to be debated and ratified before implementing and distributing it to end users. Safari is released infrequently, but when it is it only contains (mostly) solid features. However, if you value the bleeding edge and are willing to tolerate some amount of breakage, you can always install the Safari Technology Preview, which releases much more frequently.