Again, depends on what you mean by success. Do you define that only as becoming a commercially successful director? Or building a successful career as a grip, cinematographer, editor, writer, etc?
But brutal? Not really. It certainly may seem brutal if your idea of a 'path to success' is that you'll make a film, be discovered and rocket to fame and stardom, bypassing the hard work everyone else is doing - but I'd say the 'brutality' is just the collision of fantasy with reality. But that seems to be a uniquely odd trait of the entertainment industry in general - I rarely encounter people who decide they want to be a CEO or surgeon or master plumber and then expect that it's somehow going to happen without a decade or two of hard work.
This is pretty much what I was thinking reading this thread. 'Success' is a pretty subjective term, based on where you want to go with it. Do you want to be the next Spielberg? Do you want to make a good living from indy films? Become a well-connected go-to writer?
Whether you
need film school is also pretty subjective, based on you. Are you a quick learner? A work-horse? Would film school be the best structured way to learn the ins and outs of the industry and the most efficient with good connections to be built and professionals showing you every step of the way? Well... yes, it would. But that doesn't make it vital, there are ways of doing that without an academic background.
I've never been to film school, have no idea how they would structure lessons and courses, or how successful people become afterwards. But it is a professional qualification which could give you a step up. That said, you will still need to prove yourself as competent and talented, and able to go with the stresses and strains of professional life to get jobs.
My experience is medical school. This of course is necessary, legally, in order to practice medicine, but it is also hard work along the way (and after qualifying). Personally, I think some professions are more 'brutal' than film-making is. The need to constantly learn new techniques in film-making, or new rules, is somewhat piecemeal - do you really need the new technique and to be able to understand and implement it to a high level for what you do? Maybe, maybe not. In medicine it is practically a legal requirement that you constantly have to do this, as well as understand legal principles surrounding your job, knowledge of other fields, and so much more, with the emphasis on continuous learning.
So the question is: How much effort do you want to put in, and how much sacrifice are you prepared to make to get to where you want? Nothing worthwhile is going to happen simply staying in your comfort zone. If you really want to make it in the industry, then like all professions, you need to work hard to get there.