Content is King.
Google and any other search engine for that matter provide one service and one service only that is to provide a list of results from a web user query. so it is in a search engine's best interest to answer any query the best possible way. To do so search engines as Google will use programs/algorithms to visit a site and see how it may be listed on their site. For the 2019 update, Google now tries to determine the user's reputation as a writer on the content he/she provides. You do not per se have to hold for instance a Ph.D. in a field but it would help if you do and Google can find that on the web. What also counts is experience Google tries to determine that by finding out more articles of a subject matter you have written about or that you collaborated on with others. It is not just written content it can also be images and videos or even podcasts. Another factor will be back-links to your site or a specific article as well as the authority of those links, the big change this time around is the authority of the link(s) so it is wise to ensure if you want to work on backlinks that those come from good sites in an organic way, so no paid linking as well as advertisement. In short, go for quality over quantity when you try to generate/create backlinks. The next change is the user experience, how easy is to access the information and how do you provide useful content to the web. A fast responsive website that is not cluttered with advertisement and has a proper markup in terms of coding as well as the markup of the text so the end-user can read without distractions and does not leave your site and goes elsewhere. A higher bounce rate is a good indication that a user found what he/she is looking for. And finally in somewhat ties into backlinks what do other random web users think of your site and the content it provides. Reviews or links as a source are a great way to determine that factor.