My personal view is that any writer who has put in the time and effort to produce a novel should consider sharing it with a wider audience. Their story can provide enjoyment to a reader, and bring a boost of confidence to the author as well as financial gain.
However, my advice to the author who has little or no writing experience, is to at least submit their novel for a manuscript assessment first. This is a service offered by publishers, editors, and writers, (including myself), to provide comprehensive feedback on a novel’s strengths and weaknesses, and how it can be improved.
A manuscript assessment is similar to the structural editing process. It covers such aspects as the novel’s plot, structure, character development, dialogue, and quality of writing. The subtle difference, here, is that whilst the structural edit is geared towards a publishing outcome, a manuscript assessment is more about improving writing skills.
My advice to the author who has creative writing experience, is to go straight to publishing. The professional editorial process removes any barriers that might hinder the reading experience. A good editor will guide the author through the process, and highlight any areas of the story that are weaker in their presentation and may need attention.