Problem with creating new frameworks is getting them adopted.
Second problem is having that framework be able to back up its claim to the throne.
Metal not doing either. Valve and others have made open gl the middle ground between systems for years. Its also allows for headway into Linux...so in theory kill 3 birds with one stone. Apple imo would be better off making open gl better...it be the framework to be the best bridge. Hell few companies bothered to build ground up for Open gl as a start. Wrap up in some cross platform tech (ex. wine)...call it done.
And apple not even doing this in house even. Hitting on apple's home grown applications, again, these have not seen core ground up rebuilds for much of apples innovations. Swift, metal, etc.
While annoying, from a sys admin prespective since you have to push out and patch .net framework changes, its also cool when M$ pushes out revisions of .net....they actually use them. I see the cool aid, its looks tasty. But...how about you drink it first kind of thing. M$ does this.
Why should we have to use your new .net M$ asks the developer? Microsoft answers because its new, its better and 6 months from now when we release office or server product 2017....it will be using it. You can get on the bus now in dev releases and support sites or later. Either way in 6 months to a year when the execs have an idea to build up an application to interface our new stuff...you will learn this. And look, here we are being the first people on the bus.