That isn't what the sign is asking for though.
If they had hired people who didn't "actually work", then the people they hired were not putting in minimum effort.
If the sign said, "now hiring people who put in maximum effort" you would have a case. I agree that they should probably pay their workers more than the minimum wage. I'm just thinking you're being overly critical of the response that some people just go to work, socialize, take several breaks or go out back to smoke, play on their phones instead of "actually" doing their work.