Exodus 4:10 Then Moses said to the LORD, “O my Lord, I am not eloquent, neither before nor since You have spoken to Your servant; but I am slow of speech and slow of tongue.”
When God ask you to do something, it’s not because he ran out of people, it’s because its’ part of the purpose. Romans 9:20 But indeed, O man, who are you to reply against God? Will the thing formed say to him who formed it, “Why have you made me like this?”
When you don’t understand, don’t ask God questions, trust him. An excuse will not exempt you from doing what you are suppose to do.