One thing that I have noticed regarding some of the more successful SEO practitioners is that they conduct a great deal of testing. There are many courses and masterminds that exist that will tell you how to do good SEO. But what I realize is that one has to do some sort of testing once a certain income threshold is reached.
That way, one can test out theories and share their findings with trusted colleagues. And it seems to me that you will be more easily accepted into the elite ranks if you can add some sort of fact based findings to a particular group. It’s not unlike a secret society and your value increases the more you can come up with fact based SEO information, In my case, I come from a database background where decisions are made based on the data at hand. Myself, and other users of the data available to us, are able to make informed decisions, forecasts, projections, etc., based on data.
If you are an SEO, with a bunch of domains under your control, you want to be a able to come to conclusions about those domains using metrics such as Trust Flow, Domain Authority, and to a lesser extent, Pagerank. A SEO company Mississauga like the one I own will be doing testing as time and finances avail themselves. I think it is the best path to go down when at all possible.