That's the crux of the problem on land and sea too. It took 250 million dollars to repair the USS Cole from $250 worth of explosives. The land war costs are also quite asymmetric.
So we can spend Trillions (that’s what it would cost) to have all our space assets armor plated
Many are already going to be destroyed by inevitable solar flares and others are armor plated to some extent against such threats. But they key is in the sentence of yours I quoted above, the satellites that cost a billion dollars have been "obsolete" for decades, and we just don't want to admit it. As for spending trillions, that's unlikely. That calculation comes from spending a billion dollars on a satellite, it's obsolete.
Not convinced yet about that. Lots of history with 'better, faster, cheaper' where you can only pick 2 of the 3 options. Also familiar with a lot of proponents of cheap cube sats, but they have yet to demonstrate the capability of the legacy assets, either in performance, robustness, or longevity.