This all matches the advice that the first few chapters of Starting Strength give.
I think the idea is that there are important muscles involved in *maintaining stability along a trajectory*, not just in putting raw power into it, but machines do that stabilization work for you.
Depends on the goal. If you are trying to go for a specific type of physique, machines are great due to the isolated mechanical load they can place on a muscle group. If you're just going for raw compound strength, then machines are less important.