You can think of a great digital marketing expert as a conductor in an orchestra, and Website, SEO, SEM, PPC, Email, and Social Media are all essential but different instruments in the orchestra.

Therefore, a digital marketing expert is very different from an SEO (Search Engine Optimization) expert, Website designer/builder, Social media expert, or someone that specializes in PPC (Pay-per-click) advertising. While there is some overlap, these types of experts should not drive your high-level strategy. For example, an SEO expert should not drive your website strategy, because you may end up with a website that ranks high in Google but does not align with your other business or customer goals.

A great digital marketing expert will plan and oversee all digital channels for your business because your website, content marketing, social media, email marketing, SEO, and PPC efforts have to align with the overall strategy. For example, if you are trying to position your product or service as a premium offering, you cannot offer deep discounts on Facebook (Ads), and at the same time promote exclusivity on another channel (e.g. Website). Therefore most companies have a marketing manager, a chief marketing officer, or digital marketing consultant overseeing all marketing campaigns and channels. Therefore, a great digital marketing expert (or consultant) has to have experience in customer and market research, strategy, planning, execution (different digital marketing channels), optimization, and also have the ability to communicate up, down and across the organization.
You can even talk to these marketing experts and ask them if they have any references that may be suitable for your company: https://www.lindseya.com/top-50-digital-marketing-experts/
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath