Could anyone become an ATCO?
I guess the answer is that anyone can try.
I never believed that I had the necessary aptitudes (too easily distracted) and the type of work never really appealed so I never applied.
Over 40 years I worked with a number of people who had succeeded, a number who had succeeded but weren't very good and a smaller number who had failed and I was never able to see what made a successful controller.
(Many years ago I applied for a job with IBM and I had to take one of their aptitude tests. I asked the interviewer whether these tests were any good at determining who might succeed. He replied that they weren't very good at predicting success, but they were significantly better at predicting failure!)
I hope that ANSP recruiters have tests which can eliminate (and disappoint) candidates whose success is unlikely before the process has been too expensive for both parties.