It matters in so far as the production rate for e.g. air defense interceptors is much lower than the rate at which they've been used in the Iran war. Which is probably one of the reasons the US was ready for a ceasefire.

They might have enough stockpiles to continue this war for a while, but it thins out the capabilities in other theaters, making the US generally more vulnerable.

This absolutely matters. It is not 1945, and we used years of supplies.

If the decaying industrial base is that easy to fix please, by all means; go ahead and do it.

I don’t think you can fix it without long term, competent industrial policy and we have the absolute opposite of that in power currently.