You cannot teach an old dog new tricks…. forget it! Seriously forget that sentence because it is completely false. Every animal will never stop learning, even humans.
What does change is your ability to assimilate information, but it changes moment to moment, not by age. Being stressed hinders your ability to process the world and thus you ability to learn.
Your occupation hinders you as well, because the days bullshit will stop you from focussing. No, I’m not saying you should stop working. I am saying… take more down time between tasks and learn something small or a small part.
Or learn while doing “dumb” tasks by listening to audio books. Like while your driving, or gathering data from standard sources.
Learning is not a zero sum game. You can learn a whole lot in bits and pieces.