The vast majority of the time you should look for an off the shelf solution for whatever problem you face. Ecommerce platforms exist for this very reason. Typically there's a platform that matches your needs. Some shop owners need the large ecosystem around Shopify while others need the category management of BigCommerce. With the rise of SaaS it generally makes sense to find an off the shelf solution, or several, that get plugged together, for many challenges an ecommerce shop faces. Solving an immediate business problem by plugging a few separate products together is one benefit of diving into SaaS products marketplace. While I appreciate this from a nuts and bolts perspective, it's never been my favorite reason that I suggest that approach.
While I'm not sure what parts of the story are apocryphal, the Post-It Note story where a use for product has an ahha moment from something unrelated remains a favorite of mine. Most of the micro-preneur podcasts that I listen to also share that same theme. A small startup/nights and weekends project, creates a line of business out of an experiment that turns out to be more valuable than the original business itself. I love stories like that. They're unlikely and surprising, what's not to like! More practically, having small experiments and hacked together solutions allows for a environment these kinds of surprising side effects. Perhaps a series of Zaps created to solve a small problem, solve a larger one. Or maybe a second small store, run on another platform, uses a tactic that can be applied to the main stores strategy.
When you send an important email to your list, you send it to a small subset first, just in case. Maybe you're waiting to see if you get responses about grammar or testing if a signup link is broken. This is done out of habit by most shops. The same philosophy should be happening with your ecommerce site. Spin up a small brand where you use another platform. Try a different approach for fulfillment on a specific line of products. Experiment with a SaaS company that automates a workflow. Use a different agency for one part of your marketing. Try a new content agency for an agreed amount of blog posts. Of course you should keep your focus on the business that drives your success. But ensuring that you create an environment that experiments will ensure that you stay aware of new trends and solutions that might solve a pressing, expensive problem.
There are a lot of metrics that matter and there's a time and place for measuring experiments. The above suggestions should not be measured carefully. The value is in the knowledge and culture of using something new or different. These are alpha experiments. Should an idea from an experiment seem promising, then a strategy with some success metrics should be applied. That's when a shop owner should test if their intuition aligns with the outcome.