Design is the art of compressing time through visual organization. It is the two-dimensional counterpart to architecture, which of course operates in the physical world. The better the design, the faster the message will get through to its audience, and the higher the content's overall impact.
Good design saves time, but it also takes time. It's a trade-off you need to weigh before you commit to designing. It often requires continuous and systematic experimentation, along with an extensive understanding of the message's context. You need to anticipate where and how it will be displayed, and who will see it. Because everything changes, great design is never done.
You can't escape, or avoid, design, even if you wanted to. Design is everywhere, and everything. If you choose not to design, you're still designing. It's in the choices you make, and those choices will in turn lead the way to the choices your audience makes.
So are there practical solutions to tacking the problem of continuously evolving contexts and environmental requirements? How can you ensure that your design process is optimized and does not involve re-evaluating the context every single time it is needed?
The answer is to use a design system: a structured, modular approach to designing products (such as emails) which ensures that your emails are both efficient and consistent. Design is a science as much as an art. Using a design system approach, you can turn design into a process.
There is a great talk by designer Jesse Blanner (Meredith Corp.) called Creating Efficient Workflows with Modular Email Design. The video embedded in the referenced post is well worth watching in full. It may change the way you write emails. Forever.