JIT learning is a great skill to have but if it's all you do, it becomes unrewarding over long periods of time. There's something very satisfying about executing stuff that you know how to do well, and you're missing out on time spent in a flow state if you're constantly JIT learning. The quality of your work is lower when JIT learning too. Of course if you only do stuff you know well, you stagnate and get bored, so you need to balance it out.