The local pizza shop's potentially a good customer if you're selling them a way to take orders online and get people to buy their special offers and refer their friends through social media. Plenty of value in that, especially if you're yielding more proven results than those flyers they pay to have printed and delivered every couple of months. If you're selling them a homepage with a picture of a pizza and a phone number then yeah, that's what Wix etc are for.
But to use Wix Code, you will need to know some level of coding, hence value to sell for your clients.
And I agree, there is a huge market for people to build websites for customers, you need to focus on the value you deliver to your customers, from design all the way to coding, SEO, content and social.