I wouldn't say that you are too old to start learning to fly.
But, you might be too old in standing a chance of gaining employment with an Airline.
I don't know how the Airlines select candidates. Providing that you comply with their criteria. I don't think that the Airlines should be allowed to see your age on application, or even require to see it, unless they suspect that you are trying to deceive them etc...
For example, when I was 38, I had to grovel to a course leader to get onan Evening Course at College. He asked me hold I was, it made me feel humiliated and I didn't see any relevance to it!!! Especially when there were other older Students on the course.
I would like to see him again, so that I can tell him that what he was implying was wrong!! Because all of us Mature Students, have achieved much better grades than the younger ones.
So what does that tell you?
IMO you should based on merit and not viewed as a statistic. I'd rather employ someone that can bring more than flight experience to the cockpit, and most 20 year olds don't have that.
Sadly, I can’t help you with gaining employment. But I would say go for it, if you can afford to pay for it. And even if you don’t get to use it, you have still achieved something.
Best of luck.