Sure large proteins have multiple forms and functions, but we do know the exact makeup shape and function of a lot of the smaller ones, like the ones that are small enough to get between either strand of an opened helix to read, transcribe, and send for translation the code for the larger proteins (anything inside the nucleus). Saying all proteins are inherently not understandable because there are large proteins that we don't have full understanding of, is just as incorrect as saying we know every function of every synthesized protein.

Also I can't stand veritasium, he gives over simplified, easy to latch onto, "explanations" of questions and misses out on a lot of minutia that would actually lead to a better understanding of why these questions exist. But people on the Internet love that stuff because they get an answer and are enabled to say "well actually" next time the topic comes up even though they've barely gotten any of the details of the problem itself. Pop science at it's worst. Him and numberphile both