HOW FAIR IS SEO?
Google's premise of rankings and traffic is based mostly on content relevancy and content value on your site.So can you expect to write an amazing piece of content on a certain topic and post it on your NEW website that has a new domain?
According to Google representatives yes - you have great content and you can even submit the new page to Google that it crawls it does it's magic. You might end up waiting a long time for that traffic that you thought it will come.
"SEO's success, just like sales, depends on many
other factors like: marketing, product/service quality, PR, business model etc, competition level etc.
What a lot of people miss this because so many SEO's don't talk about this because it can make them look less valuable. "
Then there is another dimension that Google take into account but talk a bit less about it the "EAT" factors of your site - Expertise, Authoritativeness and Trustworthiness.
How do you become an expert in your field, be an authority in your field and have others trust you? Content won't help you here. You need links from other sites, you need others to talk about you and your site.
How big is the difference between EAT difference between Amazon or a startup? It's very big and therefore the big companies, with bigger budgets - more PR, marketing spend etc. have an advantage in SEO over smaller ones.
What do SEO's do then?
SEO's can influence how one site gets more traffic and better positions by educating the business owners how to get better at SEO and optimise the website themselves. SEO's look for new opportunities to get traffic or how to technically optimise your site that helps users.
Example: an seo tool/company Ahrefs wanted to rank 1st for an SEO keyword but no matter what they did in SEO they couldn't improve their rankings. They finally got the 1st position when they offered the tool for free and promoted it.