And also what the pay is. These jobs are overall more important than the tens of thousands of random software engineers at FAANGs.
To solve the talent deficit, they could say "We pay like FAANG. And if you do serious work, we expect stable jobs and steady career progression for at least 20 more years." Fund it by investing some of the wealth where it needs to be invested.
(The hard part I see is holding companies to career progression, so they don't just bring in people at Google L4/L5 equivalent TC, but plan for those people to become less mobile to other employers due to mainframe skillsets, so easy to retain without normal tech growth in compensation over time.)