Win the SEO competition: small websites versus big players

It may seem impossible; beat the big players in the online SEO world as a small blog or website. These websites have all the recourses they need. How could you compete against them? You can read thinks like “domain authority decides your Google ranking”, all over the internet. In this field, the big players always win. Why should you even try to spend your time, money and efforts into something that might seem useless with this enormous competition?