This Ruby meme is a variation on the common expression "One Bad Apple Spoils The Bunch" that is noting how introducing inferior devs into a Software Engineering team ends up reducing the entire team's skill and intelligence to the least common denominator skill and intelligence of the weakest links, thus corrupting the whole team the same way a bad apple gradually ruins a bunch of healthy apples when placed with them.
It's so true when it comes to Ruby on Rails development teams that suddenly make the bad decision of hiring a React.js dev for Frontend work one day even though React.js contradicts the Ruby Way and Rails Way and JavaScript is inferior to Ruby!!! The Ruby on Rails Software Engineers that were once smart suddenly become React.js code monkeys and start forgetting all the best practices and principles of Ruby on Rails due to getting used to React.js breaking them with its inferior over-engineered ways. So indeed, one bad monkey ends up spoiling the bunch!
That's why I strive very hard to avoid hiring even one bad dev on my team as I notice immediate degradation in everyone's work quality as soon as one bad dev enters a team, so we keep a tight ship on my team instead.
