It's one of those basic things. Like, when someone says "Make sure you have salt in the kitchen" they say just that, not "Open the first cupboard in your kitchen. See if there is a blue tin with a little girl in a frock carrying an umbrella" and so on and so forth.
The "make sure X is in your $PATH" is its own thing. I sympathize but there is a balance between docs for the expert and docs for the novice. This is closer to the former.
Also I'm fairly certain that an explanation of what $PATH is on unixlike OSes and how to manage that is one of the first things one will see when reading any number of dev basics/getting started tutorials. I understand wanting to jump right into writing "real" projects but things like this are why I think spending a little time finding well-written tutorials and doing them makes a big difference when picking up a new language/library/framework/etc.
There are install shields and tutorials for this. He's right, most tooling sucks and require arcane incantations. They do allow later flexibility though.
Steve Jobs if he was a programmer would slam today's tooling.
The "make sure X is in your $PATH" is its own thing. I sympathize but there is a balance between docs for the expert and docs for the novice. This is closer to the former.