> It is a better "making of" experience than any professionally produced featurette or documentary.
This shouldn't be true but, sadly, it probably is. Many "Making of"-type docs and featurettes used to actually show interesting things about how the film was made. As someone with extensive experience in video and film production, I always found these fascinating. In fact, seeing some of these as a kid strongly influenced the fact I worked in the technical end of production.
However, for at least the past decade, outside of a few trade-specific publications, the vast majority of such docus feature very little that's not obvious about how something was made. These things now focus almost exclusively on celebrity actors because they have the broadest appeal to the mass market public and such docus are funded by the distributing studio's marketing dept.
The rare exceptions are some massive-budget, effects heavy, blockbusters which already have huge fandoms where the marketers have enough budget and perceived interest to fund the creation of real behind-the-scenes, making-of content. A good example is some of content released around The Lord of the Rings trilogy which actually focused on individual aspects of production not directly involving the actors.
As someone with a lot of production experience, I should add that I disagree with the idea that "just walking onto a set and watching" is a good way to learn anything - or even very interesting. I have a tween who was fascinated by movie production, until I actually took her to some movie sets where she got to experience just how slow and boring the process can be to watch. Hours of rigging, lighting and camera tests for two minutes of shooting, which you often can't clearly see from most places on the set other than directly behind the camera, and it's rare to be able to hear any significant dialog unless you're almost in the shot. Frankly, even I find visiting a set as an observer pretty boring (other than seeing old co-workers and friends), and I actually understand and like the arcane technical aspects of production like lens focal lengths, color temps, etc. I'd much rather watch a well-produced, insightful docu which shows the gear and setups being used edited together with through-the-camera results and narrated by the technical crew when they aren't busy actually working. Unfortunately, that kind of content is all-too-rare these days and most featurettes called "Making-of..." are 90% celebrity actor/director interviews focused on the marketing team's talking points about the film slapped over a little behind-the-scenes B-roll.