Can you beat ecommerce sites with SEO

Hi
I am evaluating a few keywords to go after in my niche. Some of them have mostly ecommerce sites ranking in top 10 like amazon, walmart, ebay.

Should i completely avoid these or take a look at title optimisation, Backlinks and page authority?

I dont want to take on a keyword and it ends up being hard.

You can definitely still compete.

Yes, check page links and authority rather than authority of the domain. If it's ecommerce then get the edge by creating lots of unique content on the page you want to rank too - most of your competitors will just have same duplicated product description that was provided by the manufacturer.