I've written difficult and complex SQL, over a 20+ year period, along with taking a deep dive into relational theory via Chris Date. I'd say I fully grok SQL; well I'm still learning as are the majority of us who are not Chris Date. It's a vast and comolex topic, enough that there are experts specific to it for an entire career. Graphql is great because it's far simpler. I learned how to use it on the front-end in a matter of hours. And learned how to implement it on the backend in a few weeks. It's a different level of abstraction, and shields our front-end devs from many underlying complexities, including but not just the SQL.