You can perform your eCommerce SEO by yourself but, as a naïve SEO practitioner, you would not understand the nitty-gritty of eCommerce search engine optimization. You might know about keywords but, overloading your product pages with relevant keywords is not the right method to optimize your eCommerce store.
To make your eCommerce SEO campaign a success, you will have to perform an eCommerce site SEO audit, keyword research, and understand your competitors. You will have to work on off-page and on-page SEO, link building, content creation, and lots more things for an efficient eCommerce SEO campaign.
It is only by hiring an eCommerce SEO expert that you can drive your sales, revenue, and website traffic and find an edge over your competitors.