Oh, wow. This is a difficult topic to discuss in such small scale like here, we would have to define specific terms of effectiveness to reach a satisfying conclusion. Just so much - I disagree with their backbone being shattered, to stick to your mirror metaphor - the mirror has been cracked into several large shards, there are definitely some smaller crumbs on the ground but several large parts of the mirror are still sitting in its frame. What's important as an attacker is not how tiny you can smash the crumbs, what's important is how large are the cracks between the pieces, because that's where you want to slip through.

Since Russia still can fight a lot of aerial targets it seems that good chunk of the chain of air defense is still functional. They're still able to go through the entire chain for a lot of targets, which is a incredibly complicated process - Detection, classification, tracking, threat evaluation, fire control and fire solutions, Engagement and with missiles also mid course guidance and after the terminal phase you also have to assess the effectiveness to evaluate if you need another try to kill the target. All that works in concert with lots of information sources, different threat levels, different systems for different threats and so on and so on. A shattered backbone in my definition would be if one or several parts of this chain do not work anymore and therefore air defense becomes a game of chance. That is not what I am seeing in the reports, yes the early June attacks on Moscow definitely showed at least a partial collapse of order of air defense in the region, but since we don't see action like this every other day I would argue that Ukraine was able to surprise and saturate the air defense for that sector for that time.

I am not arguing for Russia, I think what Ukraine does with their tactics shows how well they understand the concepts of air defense and how to negate them in order to hit their targets, which is a really admirable feat to achieve against such a potent and well equipped air defense.