I belong to numerous social media groups for authors. The biggest problem I notice is when authors claim there are no rules you need to follow. That’s nonsense. If you go the traditional publisher route, they will dictate the rules you have to follow. Many times these are based on responses from readers, often from what readers are not buying.
A good example is book length in terms of word count. Different genres and sub-genres have different word count limits. You can find them using a browser search. Many authors go with it should be however long it needs to be. That works if you a well-known author. If it’s too long, I wouldn’t read it and I don’t care if it’s from a favorite author I enjoy.
Readers often have their own rules. A good example is paragraph length. Many authors go with a paragraph is as long as you want to make it. Readers and publishers tend to prefer shorter paragraphs in general. Paragraphs typically cover 1 – 3 topics. I see some advocating 1 – 6 page paragraphs. Way too long and most cover a lot more than than 3 topics.
Great rule of thumb is your paragraph should be read without needing to take a breath.
I know one blogger she thinks 10,000+ word count blog posts are okay. I rarely read most of her posts. She exceeds paragraph length on a regular basis.
Some of my blog paragraphs are longer than I like. I do try to keep them readable.