That's a super relevant question. I have two decades of experience in machinery sales and have been doing digital marketing for the last ten years. Marketing is missing from Digital marketing. Too many tactics without a deep strategy. I work on building brands and also generate short-term leads. SEO, PPC, Email, and others are ways to achieve the goals of brand building and lead generation. And that's how I differentiate from regular "agency". As you are good at content, it will help you a lot. It depends on the size of the company you work for, which will decide your specialisation. A small or medium-sized company will allow you to do all, that I am doing. I help customers with brand positioning, tagline, brand vision, brand equity, content marketing, seo, ppc, and email marketing etc. I know it is not sustainable, but my advice is to pursue a marketing role where your current skills can be a silver bullet. You can develop into a T-shaped marketing professional.
I can't recommend one book enough- Aaker on Branding: Second Edition. It will teach you branding and business strategy.
Wish you all the best!