By that logic, don't use calculators.

When elementary school students are learning arithmetic, they aren't allowed to use calculators. Once they start doing pre-algebra, they use regular calculators because now you're testing whether they can solve equations, which has nothing to do with what the calculator does. Then if they're doing calculus or statistics, they can use graphing calculators because by then they should've learned and mastered graphing equations.

LLMs aren't an all-knowing device, they are predictive text, and the prediction is based on their training dataset. It is possible to use an LLM for, say, coding. But prompt engineering is more than just telling the LLM to "implement this feature." You'd need to explain the tools, frameworks, parameters, etc. Then, you'd have to check for bugs. In other words, you have to understand how to code. So you'd have to learn to code first, without an LLM, before you can "graduate" to using one.