Maybe we're talking about two different things? To me, once you add a new feature intended to replace an old one, the old feature should be deprecated and should eventually be removed. Even if you can use AssetBundles, there's no reason you ever should because they've been superseded.
I've always thought that that is deprecation, but I could see your argument that it's not.
Fortunately I haven't had to deal with the officially deprecated features without a clear replacement. I can imagine that would be very frustrating.
> Even if you can use AssetBundles, there's no reason you ever should because they've been superseded.
You might have to use a superseded feature because you're maintaining old code. If Unity cares about backwards compatibility (admittedly, I'm not convinced they do), they need to keep supporting and documenting the old features even as they nudge you away from them.
Sure, but if that's the case, you should really be pushing new developers away from using the old thing and towards the new thing. Mark it obsolete in the editor. Update your docstrings to point towards the new thing. Maybe even give me a warning in my console if it's really serious.
I've always thought that that is deprecation, but I could see your argument that it's not.
Fortunately I haven't had to deal with the officially deprecated features without a clear replacement. I can imagine that would be very frustrating.