I have a feeling that if Adobe would publish detailed Flash file format specs when Flash started to decline, there would have been separate player implementations and Flash might still be alive today.

Of course, this also means alternative editor implementations, and this decreases business value. This is also a lot of work. And at some point, it became too late -- if format would be published today, very few people would care. So I am not surprised Adobe decided to let the Flash die, rather than open it.