As a freelancer or small development group, a common piece of advice is to focus and not try to be a jack-of-all-trades, as that hinders clients from finding you. My advice is to take that one step further: try to calculate an expected value from a technology in order to determine where to focus. But keep in mind the size of the market: while it is helpful to be a big fish in a small pond, if the pond is too small, you’ll starve from lack of food.
In probability, an expected value is found by multiplying the probability of an event with the value of that event to determine an expected ‘payout’. For software development, I find the following equation helpful: number of jobs/size of competition pool * average hourly rate, i.e., with all other things being equal, what is an expected payout for a given technology.