While it's true if you can write copy for one channel, you can write for all - your stakeholder's approach to this massively differs.
I'm a digital native. I'm not a big fan of marketing at all - mainly because my values jar against it. I don't believe you should be stalked around the internet by display ads. I hate random promoted ads appearing in my social media feeds. I can't abide pages I look at taking ages to load because of ads or autoplaying videos.
It feels there's no safe space from marketing. Wherever there are eyeballs, there are ads. And I, as a user/customer, loathe it.
My specialism is customer experience. This is a new, woolly term, but to me it's simple - it's writing and designing content to make a customer's digital experience better.
Whether it be via the UX microcopy, smooth buying or aftercare process, retention emails that offer personalised customer value, articles created to inform and/or entertain or the (non-paid) social media posts to keep customers and potential customers up-to-date, engaged or to build awareness, these all feed into the overall customer experience of a brand.
It's all about making a customer's life easier and better. A lot of it by their own choosing. It's not chasing awards or numbers, which is what marketing does.
In my humble opinion, this distinction, and trend for marketing to take over content, erodes the customer experience because it hides difficult messages, aims to amplify everything and overload pages with lots of messages.
Marketing is the maths behind the creative. Adverts are the big sell, signpost and amplifier. Digital copywriting is what happens once people hit the website and want to feel valued, respected and understood.