No. Learn something decent.
> they will probably hire any young person who has learned a minimum of COBOL
This makes no sense
> they will probably hire any young person who has learned a minimum of COBOL
This makes no sense
I've known a couple of people who worked as COBOL/mainframe developers in Europe at huge companies and their pay was definitely worse than what they could have gotten as a "a data engineer maintaining Spark" or anything else even similarly modern. The cage works both ways, on the one hand they might be hard to replace, but equally they'll have at least as hard a time finding a new job if they quit. Depending on where you live, the company you're working at might literally be the only company in that city using that particular tech stack.
What are you going to rebuild a banking mainframe system from the 1970s at home in your bedroom for fun?
I don't think it matters anyway. A 14yo thinking strategically like this will figure things out soon enough.
Being that young it would probably be best to not listen to what anyone else tells you though. Follow what you think is right and if it doesn't work out, learn from it. The whole idea could be explored and still not be old enough to drive.