Graphical schema image generation was in IntelliJ for like 15 years at least? Since the times with all the craze about UML "disrupting" software engineering.
Some fields are important for HR, others for Security, others for BI. Gotta have different visualizations for everyone.
LLM here would be like another person or another team, that decides what's important for me, what I should see and what I should not. Might work, but I'd rather see the full picture and decide myself.
Why would you need an LLM to do this? The whole point is that SQL describes it's own relationships. You literally have everything you need out of the box.