You have a bad codebase full of technical debt and bad early decisions. You know there is a way out, but it takes _time_, a good amount of time due to it's size. Time that management won't let you have due to it's ship yesterday culture. You do what you can with your re-factor as you go. People keep on digging shit in faster than you can dig shit out. They will recognize your a better developer, but when you compare yourself to the general market you are NOT a 10x developer in that place. The potential-10x developer will be one of the better ones there, but his multiplier effect is significantly reduced because he is walking in code molasses.

Because of this he will look like a medicore developer inside the that place, and it will hamper his career progression. By having to slog through crap, it doesn't push him in the right way and he doesn't improve the best he can. That is the big difference.

I think how someone else said there are 10x teams is a more accurate way to think about it. People are not islands.