Need Help with Keyword Stategies

Hi Guys, I have been lurking over here for a few months, recently I joined a DIgital Marketing Agency as an intern... I have worked on SEO a Few Websites in the last few months, I feel like some fraud now, as In everything I have learned so far doesn't work at all SEO Strategies. I tried Keyword stuffing, Researching Keyword First, and Writing Content based on it later.

Got about 5 Organic Keyword on 1 website, and that's my best so far.

is there something I am missing in my work, or are these whole Digital Marketing Training Programs are Kinda Fraud?

as these trainers said, Implement these 25 Techniques and your website will be on the first page of google, But it doesn't Work, my client page isn't even on the top 10 pages on the most Basic keyword.

I have Followed Few Courses from Udemy, then Did Nano Degree From Udacity read the book from

Exposure Ninja "How to get to the top of Google".

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I guess what I wanna ask you all is, is there any specific thing you do, which works in SEO?