It might be simple to google a recipe and follow it, but experimentation and understanding of how metals behave under specific conditions leads to better knives. More knowledge and "recipes" means a knifemaker can design a knife for a specific purpose. A one size fits all approach may yield usable knives; however, achieving a higher level of understanding and refining technique will result in more options for the knifemaker to create a knife for various specific purposes. Different steels behave differently and they require different methods of heat treatment. This is obvious. The methods to follow for each particular steel to result in a specific Rockwell hardness may be straightforward, but someone had to figure all of that out.
I'm sure with the right equipment and a recipe just about anyone could make and heat treat a knife. Would it be the best knife for their intended purpose? Not necessarily. I agree that there is a lot of hype regarding heat treatment because of advertising and marketing, but metallurgy is a real science that yields real improvements in everything from making new and improved varieties of steel to refining techniques to achieve specific goals (aka fulfilling the intention of the knifemaker with regard to the particular knife).
So while heat treatment may be a simple matter of following a recipe, someone had to make that recipe. It took a lot of knowledge and experimentation to come up with the different processes for each type of steel. Getting the most out of the blade requires that the person making the knife know which recipe to follow.
There isn't really any mystery here. It's all science. I'm sure I could make an ok knife with the right equipment and a recipe, but someone with more knowledge of metallurgy or more experience making knives would make a superior blade to mine. I don't really know what hardness is best for specific applications or what steels benefit from higher hardness levels or which steels perform better at a lower hardness. I know a little about it, but the people who put in the time to do some research and experimentation will become much more proficient and knowledgeable on the subject. They'll be able to make a better knife than someone off the street who knows nothing. They can tailor the blade to whatever task they want it to do.
This is true for just about everything. I can follow a recipe in a cookbook and even improvise a little, but I'm not a professional chef. People who research a topic and hone their craft become skilled. This is undeniable and frankly I don't see why the OP wants to argue it.