I see this question asked frequently on writing boards, and I’m at a place in my own writing to answer Yes.
I focused on short stories for a few years because I was trying to create my own self-paced MFA in fiction writing. The creative writing course that I tried in college did not move me toward my goal of commercial fiction. Dollars go a lot further when spent on how-to books, online seminars, and an occasional paid evaluation instead (I found the Writers of the Future contest valuable because I could enter for free and get detailed feedback about where I fell in their slush pile).
Short fiction is a great way to make sure that you have mastered basic skills, and that you can keep the bicycle upright and moving. It takes a complete narrative to apply storytelling lessons, and I have time to finish multiple short stories a year, but not multiple novels. I don’t think I would have absorbed information as quickly without practice. My stories from 2017 mostly fell over, and the friends kind enough to read them probably suffered. But in 2020 I completed five short stories, and by mid-2021 I have sold two of them at professional rates.
I think I’ve reached the point where it matters where the bicycle is going: whether the story concept is interesting to the reader is more important to the success of a work than my technical skills. That’s uniquely terrifying, because I can only feel motivated to complete a work if I’m excited, and I am a weirdo with a poor grasp of what normal people think about all day.
And I’m setting my writing routine aside for a few months because our youngest son has a congenital heart defect and requires open heart surgery this Fall. It’s been a chance to examine how I spent my writing time and to plan how I will spend it in 2022. When I come back it’s time to focus completely on the novel that’s about a quarter done, and send it out into the world somehow.
Of course, short stories differ from novels in more way than length. I don’t think they are required before writing a novel, but I do think they are the most efficient way to practice the entire process of fiction writing, including submission.