I have time and again fell victim to fulfill all the prerequisites before I begin to attempt to understand a topic. This is a mistake I have made repeatedly. I now understand why this is tempting to do and why it is a mistake.
It is tempting to do so because you feel things will come easier to you if you fulfill the prerequisites first. But the problem is that there is just not enough time. AND, it actually may not be even necessary.
It is a mistake to do so because you are wasting time and ultimately it may not be necessary after all.
Even in a field such as pure mathematics (I have an MS in pure Math), it is okay to skim through some of the background material and understand it intuitively or even non-rigorously, while focusing on what you want to actually learn.
It took me a while to learn that and I am glad it is being repeated here by such an accomplished professor.