If anything, it's the opposite. I have more career opportunities than ever:
1. You learn new skills -> you become more employable
2. You leave on good terms -> most of your previous companies are waiting for you with open arms (more opportunities, safety net, upper hand in negotiating salary)
3. You discover yourself -> what you want, what are you good at and where can you go next.
I would take it with a grain of salt. Contracting and living in a big city is very different to small towns and/or permanent roles.