I think this depends. You can (and should) learn things when you need them, but I have found that knowing about things before you need to use them greatly helps you when the rubber hit the roads.
Ideally I think it's a mix, where you always set some time aside (10-15%) to play and experiment with new / unknown things to sort of try to figure what they are/how they work. After that you'll form an opinion and be able to better pick thing to use when building something new and/or ramp up quickly in the learning by doing box because you've had some previous exposure.
Ideally I think it's a mix, where you always set some time aside (10-15%) to play and experiment with new / unknown things to sort of try to figure what they are/how they work. After that you'll form an opinion and be able to better pick thing to use when building something new and/or ramp up quickly in the learning by doing box because you've had some previous exposure.
YMMV