I'd actually characterize the problem the opposite way as you: there
aren't 10x ReactJS/Angular2/MongoDB/TensorFlow developers, because when we say "10x", we really mean "They delivered the same revenue with 1/10 the code/time/money" or "They delivered 10x the revenue with the same amount of code/time/money."
That usually means thinking of out-of-the-box solutions that reframe the problem in a way that's dramatically easier to solve and often more useful for the end user. For example, they may realize that your customers don't want a web UI that they have to visit separately at all, they just want to receive a text message when certain events happen, and so they can replace your entire UI team with a single Twilio API call. Or they may realize that all of the complicated algorithms you have a whole backend team slaving over can be replaced by a deep-learning network that's mostly pre-trained over ImageNet, and just needs some fine-tuning for your problem.
Usually this requires deep knowledge across domains, not deep knowledge within a domain.