Let's say someone writes a blog article. They publish it on Wordpress with a bunch of unoptimised defaults. Some time after, someone comes along and says "Hey, the search engine will rank your post more highly if you include the name of the post in the URL instead of just having it be blog.example.com/posts?id=1234", so they change the URL. Is that SEO? Should that result in the site being de-listed/banned? It doesn't meet your definition of "provide website content that is more relevant/interesting for the viewer".
And where is the line between "provide website content that is more relevant/interesting for the viewer" and SEO? If I realise that (to take an example from something found on Google) I could take the sentence "Identify the best customers and convert more" and rewrite it as "Marketing automation helps you identify the best customers and convert more", is that SEO because I'm intentionally adding a keyword, or is that making the content more relevant to the user by being more explicit in what I'm saying?
