This is a good question and one I have definitely asked myself. Compared to the newer versions of Angular, AngularJS does feel pretty flawed. On the other hand, its easier to find solutions and libraries when you come across a problem. In the DC area there are especially a lot of companies and government contractors still supporting or even building apps with AngularJS because they don't have the resources to update everything.
This just popped up in my side feed. The reason you see legacy technologies is often because they lack the requirements to rebuild the solution with more modern technologies. To do a complete rewrite, you need to perfectly understand the requirements, otherwise, how will you know that what gets written does its job? A lot of Agile teams probably have absolutely nothing describing system acceptance criteria or why design decisions were made because Agile de-prioritizes documentation. One guide I read ironically stated we should "treat documentation like a requirement"...I sure wouldn't want to be held responsible for the success of a project driven by half-assed user stories delivered by some consultant who is now selling snake oil somewhere else.
If I am offered legacy work, I tell recruiters I will only do so for $125/hr minimum. They think I am out of my mind, but I tell them they'll be paying that rate when they are forced to hire a local consulting firm to do the work. I have never had any of them take me up on that, but I guarantee you whatever number you name is more reasonable than the "expert" consultants they eventually hire who will turn around and let a junior analyst or overseas team perform the work.
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