Everybody drives a car. Many fantasize they can race at the NASCAR level, but few daily commuters would actually venture beyond their daydreams and onto a professional race track.
Everybody writes something every day. Many fantasize that they can write the great American novel. But unlike car racing, sometimes aspiring writers venture into the professional world without the proper equipment or adequate training.
What's the equivalent of Saturday night racing in writing? Regional magazines, special interest magazines, journals, or small newspapers are a good start. You may believe web publishing serves as a good training ground, but if you want to elevate yourself to the equivalent of Daytona, I disagree. Writing is a solitary effort, but publishing is a team sport. You need to learn how to work with publishers, editors, and book designers.
Publishers know the market . Even if you aspire to write poetry for a select audience, submitting your work to a small journal will build your understanding of what this select market wants and how you can better connect with them.
Many writers hate editors. I love them. They've saved me from embarrassing mistakes and challenged me to improve my work. No matter how you feel about editors--or how you emotionally handle criticism--you will not break into the big leagues until you learn to work with editors. Race car drivers may appear to be alone on the track, but the pit crew prepped their car for competition and the crew chief continuously whispers advise into their ear through a headset in the driver's helmet.
Writing is the only way to build experience, so continue to publish on the web, but also submit your work to a vetted venue. Writers want to be read. Some by the discerning few and others by the masses. You can find readers on the web, but to enhance and improve your craft you also need to participate in the traditional publishing world.