Consistent, good practice.
If you practice your mechanics routine regularly and mindfully with optimal form, then it’ll become ingrained. It’s not about how much you do it but about the quality of the practice itself. While some high level skills like animation prediction (movement reading), optimized pathing, and agent mastery only come with more hours played, mechanics are about minimizing server time when you’re in bad form to keep yourself from building bad habits.
All those top pros run drills and scrims to apply proper theory from their coaches but often individually limit-test in comp where stakes are low. Comp tends to be a very low stress environment relative to their actual jobs and is often an opportunity to test out new ideas or attempt plays without any pressure.
Edit: added “movement reading” as it’s the more commonly used term