You're dad's almost right! I say that very thing fairly often. The biggest difference between talkers and WRITERS; especially screenwriters, is whether you actually possess the determination to STOP talking and start writing.
I assure you all - we, as homo sapiens, KNOW how stories work! We've been telling each other stories for 60,000 or 70,000 years. If you look at the cave art in places like Chauvet - that was ancient people trying to VISUALIZE for their audience the thrilling wild animal hunt that they took part in or just witnessed.... or something like that. We are still doing that today with motion pictures; trying to bring our audience into the world of the hunt - and other stuff.
What writing courses or seminars can do is give you a language or terminology for telling stories. It's hard to talk to someone else about writing unless you have a common language - so classes can provide some formal names for different portions of story craft. Like protagonist, or hero/heroine - 3 Act Structure for beginning, middle and end - or inciting incident or montage. The terms that help us talk to other writers about what we're trying to do in our particular story.
The other thing a formal writing class can do for you is help you organize what you already know from years of telling your own stories to friends, classmates and acquaintances. So classes can GIVE you terminology for what you do. And the can help you SEE the inherent structure in the stories you've been telling.
And FINALLY, organized writing classes can help put you in your seat in front of the computer and actually push you to put your ideas on the page. Classes aren't for everyone; but they can provide some useful tools to starting the journey or even stoke the fire (if yours is sputtering out) for getting those story ideas onto the page when you're not sure of how to pursue your goals for writing.
And in a shameless act of SELF PROMOTION I'd like to call attention to the fact that I've JUST LAUNCHED my own ONLINE SCREENWRITING COURSE. Wordsmythe Screenwriting Essentials can really help get you started.... check out my website at www.wordsmythe.ca today!!
And this is the last time I'll do this type of AD for a long, long, long time. I promise!!!