“An open letter to my landlord”
“An open letter to higher eduction”
“An open letter to the mayor of San Francisco”
“An open letter to Congress”
“An open letter to job sites everywhere”
“An open letter in the defense of customer service jobs”
All those articles might have made a more compelling argument than writing a open letter to the CEO of Yelp. A company, that told you what they paid, in advance, and one you joined willingly. One that offered food and snacks, comprehensive health benefits and continued to invest in your training past the first month.
Honestly, the mistake that Yelp seems to have made, was to offer this type of job at all in a city so prohibitively expensive. I suspect, even if they did pay you more, you would still find a way of writing an open letter to blame someone for your situation at 25.
You may want to consider the open letter you should write, is one to yourself.