How can the examination speed of a very simple invention patent be so slow?

You can't see anything wrong from what you described. You are subjective. What is simplicity? It's been almost a year since the actual trial? Have you entered the true god? Did the examiner make any suggestions? More than a year? Is it only a year or almost two years? . . . . Or publish the patent number? The Patent Office is the most efficient department in China, and their work is obvious to all. You can't question other people's work just because of your own subjective problems. Please find out the procedural problems, do not publish the patent number, and communicate with your firm yourself. After all, patent work is a very professional matter, not as simple as smashing bricks.