The real problem here is that hiring is a giant pain for both sides. In an ideal world, you would quickly quit that job and hop to another. If you didn't do that, they would quickly hire you and both sides would move on without much stress. But changing jobs/employees is a big deal involved insurance, retirement funds, dozens of hours of interviews over many weeks, etc.

My advice for anyone in this spot is to quit quickly. I've left a number of jobs within the first month because it was an obvious bad fit. They likely weren't happy about it, but we'd all be miserable after 6+ months of me not performing how I know I can. Don't be sentimental about the work that went into getting the job, just go find a good fit.