To explain what I mean, I think you can level up a cooking style. For example, pasta. At level 1, you’re boiling dried pasta and adding sauce out of a jar. At level 1, you add your own spices. Level 3, switch to fresh pasta. Level 4, make your own sauce. And finally at level 5, make the pasta from scratch.
So with BBQ, I guess level 1 would be cooking the meat so it’s neither burnt nor underdone. Maybe level 2 is mixing different meats/cuts that have different heat/time requirements and cooking well. Further levels = ?
I think this is a good scale.
Managing the relationship between interior temperature and outside sear (without burning) is a skill worth mastering first. Like you say, burgers, steaks, and other flat cuts are easier than irregular shapes.
Another skill to improve on is smoke management. Controlling both the temperature and the quality of smoke with fuel, heat, airflow is a balance: choking off burning wood to keep the temperature from rising too high tends to produce bad-tasting smoke, and giving enough oxygen for that thin blue smoke you want can sometimes cause the vessel to get a bit too hot.
Then, being able to control all of those things (internal temp, external temp, smoke quality) over a long enough period of time to cook tougher cuts is an increase in skill/difficulty. Smoking chicken might take an hour, while smoking ribs might take 3 hours, and smoking brisket might take 12+ hours. Some cooler cooks, like cold smoked salmon, can be challenging, too. Getting a feel for adding fuel to a cook and how to do that while maintaining the same steady stream of high quality smoke of the right temperature requires some experience.
Which also isn’t to say that there isn’t some room for a high level of skill on short cooks. Working with embers and wood and flame to make short cooks over high heat can be challenging, too. Smoked or wood fired vegetables are especially interesting, as some introduce moisture control as an element, over time frames short enough to precise timing starts to matter, too.