You are confusing regular reserve and BARS active. The former is like 25-30+ million. BARS are already in Ukraine, the plans are to draw from ROTC grads and the regular reserve. I don’t see a problem. The idea that everybody in running away is simply ridiculous. I doubt if any of them is going to see action until spring. And then they are likely to stay home to warm chairs for regulars who’d get deployed.
By Spring, there will not be the need for new Russian missile fodder.
The war will be lost in total by that eventuality