Controller shortage is worldwide. NavCanada being blamed here but US is suffering, Ryanair has a constant campaign against the issue in Europe and the gulf states are hiring.
When Covid hit, ANSPs were under huge pressure from the airlines to freeze recruitment and training but it’s a long process in ATC from recruitment to validation, often 4 years, and airlines don’t seem to fully grasp that.
If management at (any generic low cost operator) successfully lobby to cut ATC charges, they’ve often moved on (with a hefty bonus) before the problems arise.
We’re back at 2019 traffic levels with fewer staff and a bleak outlook because of retirement forecasts and training lag.