There is a big difference between being a hobbyist/amateur and a professional. I have a couple of "mantras" or words to live by or whatever when it comes to professionalism:
The difference between an amateur and a professional is that the amateur learns from his mistakes, the professional learns from the mistakes of others.
The professional knows that the minute he stops learning he is no longer a professional.
There is just too much to know when it comes to filmmaking. If you're making films for fun then do them any way you want. But if you want to make films for a living you need to approach it in a professional manner.
The biggest problem, as I see it, is that fledgling filmmakers attempt to do way too much. Just off the top of my head - and remember that I'm exclusively a sound guy - you need to learn to how to frame and block a shot, and how to light it. You need to learn the full capabilities of the camera and lenses, and how minute changes affect the look of the shot. You need to learn sound technology and technique, and how to boom. You need to learn how to edit, how to do audio post, how to do CGI, how to color grade. Then, of course, there's securing locations, insurance, budgeting, casting, scheduling, marketing and other details.
Oh, I forgot something minor; you have to DIRECT the film.
There are people whose entire lives are dedicated to just one of these crafts, and fledgling filmmakers somehow think that they can read a book, browse a forum or two, and they can master everything there is to know about filmmaking in one swallow, buy the right gear and it will work automatically. Sorry, it doesn't work that way. It took me more than five years before I felt I really had a solid handle on audio post, and I was an experienced recording engineer before migrating to sound-for-picture.
So if you want to be a professional you should be working on films sets. I know that this flies in the face of a lot of advice around here, but in my opinion you don't just dive in and make a film. You need to learn and understand techniques, watch professionals at work - learn from the mistakes of others. If you want to be a director you should have at least a passing knowledge of each of the crafts and "speak the language" so you can communicate efficiently with your department heads.
Get your ass onto a film set and do a job - PA, gaffer, gopher, grip, boom-op, extra, props, driver, AD - or any of dozens of other craft jobs.
The point that I am trying to make is that there are dedicated professionals whose entire being while on set or in post is to make your life as a director easier and to provide you with the freedom to be a director. Wouldn't you love to have a 1st AD or line producer who handled all of the logistical details? How about being able to tell a DP, or an H/MU, or a set dresser "I want..." and then be able to move on to working with your actors? Sounds good, doesn't it? That's what all those folks listed in the credits do - they are extensions of the directors creative vision. And great directors know that the people who work for/with them may have better ideas and are willing to incorporate them, or at least listen and try it a bit before saying "No" - budget permitting, of course.
To top it all off, you may find something that you love doing and make that your career. One of the most famous examples from film is Jack Foley. Jack was a picture editor in the early 30's. When there was no one in the sound department was available to replace sounds under Looped (ADRed) dialog he did it himself. He codified the process of replacing human created sounds during audio post and put together the first facility dedicated to the process. The industry honors him for it by calling it "Foley." He did well over two thousand films.
When I took my advanced Pro Tools courses for music engineering they also offered four weeks (eight eight-hour classes) of audio post for only an additional $200, so I figured "Why not?" I liked it so much that it is now my profession.
Well, I really got off on a tangent, didn't I? To put it into a nutshell, there are dozens of talented crafts people whose entire job is to serve the director, so the director can DIRECT.
