@eater
there are also products built on top of those three, like WooCommerce, Shopware, … When customers come to you with “I want e-commerce!”, they expect you to recommend a product you are already fluent in, so that you can tell them why it’s a good fit for their project and how they should set things up. In those projects, it’s really hard to learn-as-you-go.
Of course there are other types of projects, where you have more freedom. So it depends also on what things you want to program.