When you start a novel, you begin to work on selling your protagonist to the reader. They have to want to like the protagonist or care about what happens to them.
When you write a query letter, you have to work on selling yourself in the same way. Make the agent or publisher care about you or care about what happens to you.
That part is in their hands. Do your part right.
If you spend a thousand hours writing and editing a novel, don’t spend 15 minutes writing your query.