ATC watcher; thaks for signposting where we can get some professional views on what the state of CAT is likely to be over the coming years. Of course, these forecasts are based on many assumptions of the future and so the figures could be better or worse, however, I reckon it's better than most pprune armchair analysts could do.
Unless I've misread the latest Eurocontrol report, it looks to me like Europe is currently at 35% of 2019 levels rather than the 21% you have quoted. Also, Feb 2021 is forecast to be at 75-85% of 2019 levels, and if the current trend line on that report continues it should be closer to the upper end.