There are two traps people can fall into, when it comes to new technology. One is to jump on anything new and use it no matter whether it’s suitable for practical purposes and the other is to never spend time on stuff you can’t use productively.
You seem to suggest the latter to be best practice.
While it’s undoubtedly more effective to learn something while applying it in practice, there is actually value in spending some time with tech that you can’t use productively right away. It helps stay on top of the game. You get to know which technologies are out there, get to know new ways to solve existing problems and you get a chance to acquire skills that will be important in your next job.
The important skill to acquire, though, is to know when to spend time with something to learn and when to use a new technology productively.