Good programmer can switch niches and will still be a good programmer, there's no doubt about it. Problem is that it still takes some time. You can't just pick

Good programmer can switch niches and will still be a good programmer, there's no doubt about it. Problem is that it still takes some time. You can't just pick up a new language (or even just a new framework) and immediately start producing your best code. It takes time to pick up the style and best practices, and to learn all the nuances. Also very importantly to embrace that new mindset, which can be sometimes hard when you've been doing something in a particular way for long time. There's always that warming up period where you instinctively still try to stick to your habits from the previous language, and you end up with Frankenstein looking code for a while.