Is there really a point of sending a message to your MP?

I saw some posts about emailing MPs about certain issues (RTO, WFA, etc.). First I was curious if this was allowed as a federal public servant. Then when it seemed okay (in certain parameters), I thought I would write a letter for WFA. Once I finished, I thought of the letter responses I have drafted in my role and just thought was there really a point... like what is one letter going to do? Even if it was 10,000 letters, doubt it would make a difference. I remember a union campaign when RTO was announced and I think 25,000+ letters going out and it did nothing. Most people didn't even get a generic response back from what I heard.

As someone relatively new to the public service, I wonder has this ever worked? Are there some success stories? Should I just become cynical now?