When I was first breaking into the field I was also forced to work with legacy mainframe code. It was a nightmare. The code was horrible, the pay was low, and we had no respect. I spent a little over a year learning Ruby and JavaScript in my spare time, joined a startup, and have had a happy and successful career in the many years since.

I can only speak for myself, but the transition improved my life immeasurably. I can't even imagine how different things would be if I had stayed. Keep at it. If I can do it then you can too.